Looks like nothing has changed. This is how it opens up on 4k screen. Although, it looks like they tweaked it a little. Up until recently I remember opening a post would show a hilariously small like 800 by 600-something box, half of which was comment section that'd fit like 5 comments at best. But now they finally made it properly scalable.

That’s because they didn’t make an iPad app and so it was just the iOS app on a large screen. Lots of app used to be like this until they made iPadOS versions.