I'm admittedly new, but I thought that was the difference between Hot and Active.
Active is for any activity, so comments on a 3y post are fair game. It's actually kind of a cool filter that offers the classic "forum" style that revives old posts, rather than the reddit style of "anything older than 12 hours is dead to everyone"
I think if someone went all out with making some sort of bizarre simulator game like this, people would play it. Like, don't even try to make it fun or add a story or anything, just make it as real as you can.
I don't think it's entirely the app. I've had it happen to my Lemmy.world account using Jerboa and Connect, so I think this must be them working on stuff after the hack.
I say the more the merrier. I'm still going to use startrek.website, but it's good to have a presence on other instances to avoid becoming reddit.