Just require people submitting a bounty to post an evaluation fee. If it's a real bug they get a refund and the bounty. If it's AI slop, you keep the evaluation fee.
You don't have to determine if it's an AI or not. If AI finds a real bug then it can get the bounty. If a human pays to make you read artisanal hand-crafted word salad then they don't get a refund. Real bugs get the bounty, imaginary bugs pay the fee.
This might work but only if the evaluations are done through a trusted third party entity where none of the money ever reaches the company you're submitting to.
You only need things like that for non-iterated games. A company that gets a reputation for keeping the money when it's a real bug would stop getting real bug reports.
The number of problems this creates absolutely isn't worth it.
You've traded higher barrier of entry for a PR nightmare when someone publicly complains that you ate their legit submission fee as a money grabber.