The game is free to try and then you unlock it with an in app purchase. You get quite a few hours of gameplay without having to pay up front.
It is a fully fledged game though, not your typical mobile trash.
AC Shadows will likely have a similar model since it’s supposed to play on mobile as well.
I’ve seen this everywhere, not just with Lemmy apps. It appears to be an iOS bug. It’s more prominent when I am AirPlaying to my sound system.