Hmm. The 6502 is/was often set up to access the memory only half the time. For example a 1MHz CPU would be interfaced with 2MHz memory, and access every other cycle.
I've been watching his videos for a long time and as far as I can see, the goal is never technical sophistication or doing things in a "production ready" way. Rather, it's making the innards of a computer understandable. The way that he did it here, he could easily explain when and how the CPU had control of the bus and when the video card did _and_ he had a picture that he could point at to visually explain what was happening.
I've also noticed that he'll start simple and then layer on more complex things as the series progresses. No idea if he's planning on doing that here, but a good example was with the 6502 computer where he implemented it out of the gate with no RAM so that the video could focus on getting things up and running.
https://en.wikipedia.org/wiki/MOS_Technology_6502#Technical_...
I guess Ben knows this, but avoided it for some reason. Perhaps interleaving the timing on a breadboard isn't that easy? Never tried it myself.