I had no idea it was so strict. I just use Firefox. Their cookie behavior must be picky enough that it bypasses whatever nonsense Twitter is doing?

After posting that, I went back and retested. It looks like they have swapped back to a soft nag popup. For a few months it was hard blocking any further scrolling, at least with Chrome.

That's quite possible, I did move to nitter for a while, some months back, due to that.