We are discussing what someone would use when writing about a hypothetical person.
And that changes it how? It's insulting to misgender someone, though I can understand how you'd think that there's no harm in insulting someone hypothetical.
I suggest you do some research on the history of language
Per your suggestion, "they" has been used to refer to a singular person since the 14th century. "He" is currently masculine-only. I apologize if you misunderstood my use of "never" to refer to things around the 18th and 19th century (when it apparently was considered bad to use "they" in the singular) when I presumed that there was an implicit limit to modern usage of English.
A bit of a strangely organised article. The relevant information is actually near the end of the article, with the start just providing general slaughterhouse tactics. Here's a summary of the relevant info:
Unfortunately the original order makes it very annoying to read if you don't care about the website's agenda. They'd probably have more success in reaching other audiences if they skipped the general slaughterhouse tactics part since it isn't about avian flu at all.