I found this elsewhere and it seems to clear up the issue, for me at least:
The new “Remote Watch Pass” is primarily for users who stream from servers owned by individuals without a Plex Pass. For example, if your friend runs a Plex server but doesn’t subscribe to Plex Pass, their remote users will need a Remote Watch Pass to continue streaming after the changes take effect. Because you have a Plex Pass, your remote users will continue to be able to stream from your server remotely without needing to purchase the remote access pass.
And just found this from the FAQ on the announcement page:
I do not have a Plex Pass, but stream remotely from a Plex Media Server:
To stream remotely starting on April 29, 2025, you will need a Remote Watch Pass or Plex Pass subscription on your account or the admin of the Plex Media Server from which you stream will need a Plex Pass subscription on their account.