So the fixes are still fixes, but we (I am also a OSS maintainer) are unwilling to accept them as they boost the contributor’s status where we think the merit is very or extremely limited. Why not have these PRs counted differently (by the platform), and/or colored differently in the timeline(s) thus made less visible or more clear?
I don't think that there is a technical solution to be found here, as the problem is anything but technical.
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A hack/trap:
Comment "Ah yes thanks a lot for the hint :)", then make the changes yourself.
Then see how the person reacts to that.
Hack the grifters. Hack the planet.