This isn't something I've noticed before, but I now see that if you aren't logged into Twitter, you don't see the latest posts on profiles.
For example, not logged in (top unpinned post from 2022):
https://imgur.com/a/t3D2NaD
Logged in (top unpinned post from a few hours ago):
https://imgur.com/a/dAgKO1g
Is this something new or has it always been like this?