if you open it full window/in youtube app you can see the description about this project in the second video that is linked here... it mentions screen 4, as well as some more details/info about his code.
Otherwise the black corners in some of the tiles of the first video are a giveaway
anyway, ive seen a few of his older videos and i think its cool and very inspiring/motivating to code myself
The main problem of the fake dual scroll plane is that limits too much the graphics you can make, as the background must be made of a set of coincident with foregroud pre-shifted tiles.
I'd prefer to use the memory i.e. for animating the main non-limited (free design) set of tiles.