Certainly the whole thing is awesomely bizarre, so not criticizing the choice. It just seemed to make things more impractical since it adds the requirement of the "play" button and pressing keys on both machines and waiting for the load on startup instead of just turning them on.
But then again practicality isn't a high priority for this thing.
I'm guessing he's using a variant of his own Qwertuoso program for the playing, and it's tiny, less than 4k. Even with the horribly slow default C64 tape loader, that would be about a minute.
Linus is one of the demoscene's experts on fastloading too, so he may not use the default loader!
But then again practicality isn't a high priority for this thing.