Wow I’d never heard of anything like that before, that’s pretty dang cool.
I know some Minecraft mod packs used to have pong integrated in their loading screens.
Small history lesson for those interested: the reason we didn’t see much of this sort of thing is because Namco actually had it patented, up until late 2015. Originally, you could play Galaxian while you waited for Ridge Racer to load! (At the expense of everyone else being able to have little loading screen games…)