There is one in that list for OpenBSD kernel in 2016. When tmpfs was removed from OpenBSD the reason given was "lack of maintenance". The problem found by afl had nothing to do with the decision?
My guess is that it was something like:
afl-fuzz: There is a bug in tmpfs
openbsd: Ok, who's responsible for fixing tmpfs.
everyone: ...
openbsd: Ok, no one is maintaining it. Let's go ahead and disable since there are alternatives, and no one is providing maintenance.