Looks like something done on the archive site end.
I'm pretty sure the non-mobile version of twitter shows less responses, so it's a feature not a bug.
More and more sites have this thing where you have to scroll down or click something to see the content and I think sometimes it's intentionally to prevent archiving, but I had to buy a new wardrobe because I ran out of space for all my different tinfoil and aluminum fedora's, so what do I know?