On the other had, most educators find kindergarten to be indespensible
That's my general feeling as well.
I haven't thought that far ahead, but I have a feeling that I would get more resistance skipping K vs skipping preschool.
Many of the eduacators I've met also resist the idea that you can learn, say, third grade math without having gone through the entire third grade book. There seems to be almost no concept that a child can learn these ideas very well in a non-typical way or that some kids don't even
need instruction in some of the topics in that third grade book.
FWIW, my DD skipped K and it was easy to prove. They just gave her end-of-year tests, which were a cakewalk for her. As the kids go through higher grades, the tests may be a bit harder to ace when you don't know a thing about the curriculum they're based on. For example, a social studies test might depend on knowing certain facts that your child hasn't been exposed to. IMO, it's harder for a kindergarten-level test to include things a HG+ kid wouldn't have acquired through giftie osmosis.
