Eh I mostly agree with you but if you really expand the scale of it all I think it starts to at least make a little more sense why some smaller groups pop up now and then raising awareness for one specific proclivity or the other. Actually it has a lot to do with what you just expressed I think.
It sounds like your opinion about preference and rejection comes from a place of self confidence. That's a good thing but I'm sure you can imagine how that could be harder for people who don't understand themselves and their own feelings as well.
For many people, sexual preferences are not a big personal issue that will cause them a great deal of stress in their day to day life. For some, the very fact that they do not align with their peers can make things really uncomfortable and uncertain especially around the more formitive years of establishing who they are as a person even just in their own mind.
Even heterosexual people have to achieve that introspection but we get the benefit of having lots of personal relationships with similar leaning people to build our frames of references.
Sometimes that is also an optuion for the more common non-heterosexual variations but that is mostly thanks to the greatly increased social presence which has the simultaneous effect of reducing the general stigma around such topics.
The more successful these groups oh like minded people become in projecting their influence the less they need to do so but most of the groups who championed these causes over the last decade or so realized how powerful an impact just growing awareness had for so many people that would otherwise have no support from their peers and while it's not quite as necessary to raise awareness as much for the most common members (the L-esbians, G-ay, B-isexuals...) the rest are still trying to catch up with the leading edge of the awareness movement.
TLDR, the spreading of broad awareness isn't so much about labeling themselves for people who don't care as it is for the benefit of others who feel the same way but don't know they have peers that can help them understand themselves.
It certainly matches up with my ADHD experiences including a past relationship. First diagnosed at 24 or maybe it was 25 and being rather sociable I met people through whatever my particular interest was at the time. Tennis, ju jitsu, volleyball at the park, biking, frequent gym routine, hanging out at a local bar. Most of these were pretty active things until a jackass in a blue gi messed up my knee and slowed my physical activity down considerably for a while.
Girls I met who were really into one active thing were usually also on board with trying another active thing even if it didn't stick for them but I started to notice a difference between our philosophies on hobbies and interests.
A byproduct of ADHD for many is the ability to learn and acclimate to a new interest really fast and it wasn't long after my diagnosis that I came to understand my frequently changing interests were replacements more often than they were additions.
When my knee became an issue I got really into cooking, then magic the gathering, then D&D and other table top games, and pc gaming in general. The girl I was dating at the time helped by being a really good point of reflection as I jumped from interest to interest and she was struggling to follow despite still enjoying each other's company. She liked that I was enthusiastic about things and loved that energy but since she wasn't able to share my new interests as well it strained our relationship a bit.
I was in therapy with a great doctor regarding my adhd diagnosis still at the time and she helped me through the stages of grief that often comes with ADHD diagnosis. Realizing that despite my efforts I will not always be able to control the way it changes me, my perception, and expectations of others I came to this understanding of self made rules when interacting with partners who do not have ADHD:
I must be clear about my opinion on tasks and topics early. I must make sure they understand my experience through the lens of ADHD is likely very different from theirs. I must communicate how a thing feels calmly when the context is still fresh in their mind. I must work with them to establish a fair system of equal compromises because neither of our own ways is more "right" than the others in most circumstances. I must try to recognize when I am facing a task or responsibility that my disorder will make me resent completing and I should share that feeling and explanation with my partner whenever I can.
Keep in mind these are some psychotic "I must always obey these internal rules!" kind of things but rather they are helpful reminders that I am not the imagined high energy, happy go lucky person I sometimes come off as and being up front about my quirks helps set the right expectations in a relationship. Not everyone can deal with an ADHD partner and it's shameful as well as harmful to yourself to try and trick them otherwise even if you do it with good intentions.
You do not need to feel ashamed of false advertising because with ADHD, it was never really your choice. Even in this post you still wish you could enjoy that interest but the fact is, you don't and that really sucks because it's one of the things ADHD has robbed you of.
If you are just about to get your diagnosis then make sure to get into some therapy too along with medication if you go that route as you will likely start learning a lot about yourself now that the mystery of your nature is made more clear.
Its like putting on glasses for the first time if you grew up with bad vision. You never knew how many details there were in some things ubtill you could see them through new eyes and once you start to learn more about ADHD and you can recognize things in your life enough to ask "is this a me thing? Or is this an ADHD thing?" you will gain a much broader perspective.
Oh and to answer your final questions, yes this sounds a great deal like ADHD to me with a healthy dose of strong introspection and unfortunately medication does not treat this part of the disorder. The meds are a crutch to help you focus on things you don't want to focus on naturally. Everything else will need to be treated by you learning about what makes your particular brain tick the way it does.