This is broadly what reasonable people believe, but there are crazy people who WILL obsess over form and nitpick your whitespaces or other trivial bullshit if given a chance. An authoritative style guide shuts down many such detours.
It's not even just about obsessive nitpicking. There are people who, for example, prefer code with spaces around the parens for conditions and people who don't. If there's no enforced style guide and one from each camp end up touching the same code, you're likely to get a bunch of pointless noise in the diffs. Even if no one is going to hold up a diff arguing over it, it makes it harder to review changes.
