I use a search engine that isn’t in the list (Kagi). I have to use an extension, but it works fine. If Apple was squelching competition on Goole’s behalf they certainly wouldn’t allow that.
Apple clearly weighs lots of things when making decisions on behalf of its users. Privacy is import, but so is best experience for the majority of the users who will never change the default. I’d argue Google, while a shell of its former self, is much better than all other options with the exception of Kagi - and they’re never going to set a paid alternative as the default.
So Google makes sense. As I said before, I suspect Google would be the default even if Google didn’t pay one cent.