traded in for more consistency and less friction over everything code formatting
But this sounds like a pretty theoretical problem to me. Do we regularly have review friction over the kinds of issues that humans and formatter might disagree about (e.g. how to exactly align a continuation line)? In my experience those are just left to the author as long as it looks somewhat sane. The only style comments I usually see on reviews are unambiguous things like line length or brace placement, where the formatter will do the right thing when it's configured right.
Why not try making it optional first and see what friction remains in practice?