Honestly, my view is that this is a technical solution for a cultural problem. Particularly in the last ~10 years, open source has really been pushed into a "corporate dress rehearsal" culture. All communication is expected to be highly professional. Talk to everyone who opens an issue or PR with the respect you would a coworker. Say nothing that might offend anyone anywhere, keep it PG-13. Even Linus had to pull back on his famously virtiolic responses to shitty code in PRs.
Being open and inclusive is great, but bad actors have really exploited this. The proper response to an obviously AI-generated slop PR should be "fuck off", closing the PR, and banning them from the repo. But maintainers are uncomfortable with doing this directly since it violates the corporate dress rehearsal kayfabe, so vouch is a roundabout way of accomplishing this.
If that worked, then there would be an epidemic of phone scammers or email phishers having epiphanies and changing careers when their victims reply with (well deserved) angry screeds.
This is the level of response these PRs deserve. What people shouldn't be doing is treating these as good-faith requests and trying to provide feedback or asking them to refactor, like they're mentoring a junior dev. It'll just fall on deaf ears.