If you casually ask this while you can study (and preferably record!) the person's posture and they react in real-time then you can apply interrogation technique which CIA et al use.
So becoming an open source maintainer will involve an in-person trip to an interrogation?
The xz attack involves, in significant part, a maintainer burned out and happy to accept offered help. I don't think making it substantially harder to receive genuine help is likely to improve the situation.
I just wanted to bring up that technique (it is not unique to CIA; LE also uses it). I never asserted the technique would've been useful in this very situation. However, in your framing you ignored the option of video conferencing.
Also, you are forgetting bringing up 'are you trying to pull xz to me?' is a yellow flag towards the person who said it. It isn't definite, it just makes people raise up, it gathers the attention of watchful eyes. We should be careful not overdoing it though.
I made the original comment and must say that it was only meant as a joke. But, maybe some cases would merit using it.
This is of course based on the fact of how the xz attack needed a couple of apparently innocent community members to start being too pushy, to the point of almost bullying the author and pointing fingers to their supposed passivity towards maintaining the project.
To some levels of such behavior, after all that has happened, one could reasonably (even if just jokingly) wonder if it's not a similar attempt. IMO, being framed as a possible attacker would probably either calm the shit out of some too entitled users, or provoke them into even more whining.
Now seriously, there is the thing about attitude that I wish was more popular among FOSS maintainers in order to have a mentally healthy relationship with their role: the ability to work on their own terms and not forget even for a split second that this is all a hobby activity. That FOSS licenses are explicitly written to allow A LOT of freedoms such as hiring 1st or 3rd party support services, forking, or whatever else but not to demand anything from the author.