Ah, sorry, I think I mixed that up with the opposite practical limitation then – IIRC you can't actually display a fullscreen bitmap on the original GameBoy wit

Ah, sorry, I think I mixed that up with the opposite practical limitation then – IIRC you can't actually display a fullscreen bitmap on the original GameBoy without some hacks, as the full screen fits 360 tiles, but there's a limit of 256. But in any case a frame buffer would use up almost the entire available VRAM of 8 KB and would have probably also been more expensive since it would have to be dual-port RAM (I believe the Game Boy's VRAM isn't).