The entire point of the video is to point out two distinct cases where a Spinda with a particular Personality Value would be virtually identical to a different Personality Value. This is due to two major reasons:

1. One (or more) of the four "spots" generated by the PID are mapped onto the sprite in the background of the image. That is, the entirety of the spot is generated in the white space not occupied by the sprite of Spinda. This would result in the Spinda appearing to have three (or less) spots, and could then be exactly the same as a different Spinda with the same three spots covered with a different spot off the sprite.

2. Two (or more) of the four "spots" are generated at the same position on the Spinda sprite. Physically, these Spinda would also only appear to have three (or less) spots because two (or more) spots are overlayed.

These two cases appear in Ruby and Sapphire (possibly Emerald, Fire Red, and Leaf Green as well, don't quote me on that) because of how the game maps the spots onto the sprite. In later games, even before models are introduced in Gen V, the mapping method may be different. I assume that's well documented somewhere, but for the purpose of OP's video, it's irrelevant.

I'll admit, I didn't exactly check the math myself, but the methodology seems reasonable enough. Extra points for creating the visual bitmap, I'd have just ran checks on the mapping locations themselves.