I believe their logic is such (I'm not involved with the study, but have a background in medicine and research):

Elevated PSA (a blood test) signals prostate cancers.
PSA tests are relatively routine bloodwork with an assumption of uniform coverage across all patients, trans or not. PSA tests are presumed to uncover early cancer presentation. Therefore, if we're only seeing advanced cancer presentation in trans women, the PSA test is a poor screening device for early prostate cancer in that population.

Point 2 is a big assumption; I am ignorant if that would be a confounding variable in real life, or if that's even been studied.

For what it's worth, if you post a story (for example) to the open internet -- your blog, social media -- and there is NOT a paywall or explicitly restricted access, many (if not all) publishers will consider that material previously published. That doesn't mean it's public domain at all, but it does recognize that the work is not private. Likewise, I'd consider any social media post being akin to posting a sign in my front yard. If someone does the work of driving by and taking pictures of the signs in my front lawn, that's their right -- unless I'm in a closed, gated community.

Then again, i see people thinking that they somehow "own" their Facebook feed, so ....

They're getting two birds with one stone.

The effect would be felt by both LGBTQIA+ clubs and GSA's in the schools, at a bare minimum. They would be unable to utilize the pride flag, for example, in any kind of advertisement, logo, banner, etc.

Unlike? I think you mean they're JEALOUS of TikTok's appeal to minors...

I get this argument... but I keep seeing folks talk about Threads as if it's somehow an existential threat to Mastodon rather than "big crappy instance with asshats on it," and I don't quite understand how it's more than that... at least at a level that users and instance admins have any influence over. Can someone ELI5?

Dude, I mean high school clubs advertising to other high school students, like this one: https://www.coolidgeshs.org/ourpages/auto/2023/5/3/45488112/image%20_2_.jpg

Oh, neat! Thanks for pointing out the USA centrist viewpoint I had there! My bad indeed!

Right, but that's what the language of the bill is intended to silence.