I think these concerns are a bit overblown, as our twins watch the living hell out of YouTube kids and I do check it periodically. They tend to find families or series they like and stick with them, and mostly it’s the typical “family that unboxes a lot of toys and videos themselves on vacation and adventures” sort of stuff like hobby kids, for example, which they love:
I guess if you were just randomly searching and hit the weirdest edge stuff, but I dunno. The weirdest thing I’ve seen them find on their own was this BBC doc on the world’s tallest children but that was 100% legit, it’s a BBC doc for kids.
They do a lot of voice searches as well, but I audit it periodically and I’ve never seen anything untoward.
That said, it’s always good for Google to tighten the noose on this stuff if there are weird things (particularly copyright-infringey-things, you’d think they would be on top of that anyhow) slipping in around the edges.