Similar to the PR descriptions, I'm concerned that a tool like this would create an illusion of security against the "simple" problems (leaving reviewers to focus on the high level), whereas I'd hope that the human reviewer would still read every line carefully.

PR descriptions should be about intention, not what changed (what changed is in the PR itself), so I agree there.

With the other stuff though, if you treat it as a linter, that might be fine? The problem is when you justify getting it as it'll save you engineering time, but it won't actually do that significantly unless you have a lot of people using it.