James has a whole other channel for non-sims stuff. He actually posts almost as frequently as lilsimsie, but not as much on Sims Stuff.
As for Planet Zoo, I do think they contacted several prominent Sims players and gave them copies and not just those four. Several of them were also given behind the scenes experiences at the San Diego Zoo as part of Planet Zoo's promotional lead up when they were all at an event in the area. (It's also a very cool game that I need to play more.)
But seriously, I think you're seeing patterns where they don't exist. Humans are good at that. I only follow six Youtube Simmers myself - those 4 and two others, mostly for Build tips. All of them had a flurry of tiny builds after Tiny Living. Sometimes one will see what another does and think "hey, that's a good idea, let me make my spin on it" and sometimes it's spontaneous parallel creation - happens all the time in movies and writing. Part of why in the US, you can't copyright an idea, just the expression of that idea.
