They should ban this or else they will get swallowed up and companies will stop working with them. The last thing I want is a bunch of llm slop sent to me faster than a human would
As long as they maintain a history per account and discourage gaming with new accounts, I don't see why anyone would want slop that performed lower just because the slop was manual. (I just had someone tell me that they wished the nonsensical bounty submissions they triaged were at least being fixed up with gpt3.)
HackerOne was already useless years before LLMs. Vulnerability scanning was already automated.
When we put our product on there, roughly 2019, the enterprising hackers ran their scanners, submitted everything they found as the highest possible severity to attempt to maximize their payout, and moved on. We wasted time triaging all the stuff they submitted that was nonsense, got nothing valuable out of the engagement, and dropped HackerOne at the end of the contract.
You'd be much better off contracting a competent engineering security firm to inspect your codebase and infrastructure.