As far as I know, Twitter has always done this since the "Likes" were introduced. I don't think they're recorded in a permanent manner on who liked what, just the total number of likes per post as a counter.
Surprisingly it does show these posts on your "Likes" page in your profile. But they aren't marked as liked, and liking one will increase the like indicator.
The UI optimistically allows the user to tap/click the like button and the eventually-consistent backend determines if the like is valid. The UI doesn't verify if the user is allowed to like because that's the backend's job.