How do you enforce this?
In this case, this is coming from Oracle, which holds the OpenJDK purse strings, so being found in violation is also likely to have financial consequences for the violator.
Asking how do you enforce a policy that is practically unenforceable is a legitimate question.
Mostly after the fact when people get caught. It's hard to enforce is rarely a good argument against a rule.
Regardless, some efforts like this are explicitly performative. In the event some problems arise and it turns out someone used a specific tool in the process of causing those problems, administrators (and insurers) can say "look we forbade the use of that tool, so this is on them and not us." In other words, enforcement is not always even the point, but it always seems to be the first stop on the concern-trolling trolley.
Finally, yes, people can misbehave and break rules, and the more effort they put into doing so, the more successful they will be at the rule breaking. Nothing about that is justification for not having rules, even when they are hard to enforce.
Well, because it's going to lead to witch hunts and drama and so on. I mean, not necessarily on this project, but the same-ish discussion is going on on many community based projects (debian was recently on the front page with 4 proposals, etc).
Or like in the case of checking that free range eggs are in fact free range eggs.
Or like in the case of Steam demanding AI disclosure, to the dismay of Tim Sweeney ...
Let's hope the dismay increases over time.
It's not impossible - right now there are all these low-effort PRs. If the PR is indistinguishable from a normal human-written PR, that addresses some of their concerns.
In any case, a rule or policy that can be worked around is not a reason to do away with that rule or policy.
I mean, if we only ever catch 10% of murderers, do you really think it is reasonable to remove that law from the books?