A fuzzy issue of responsible disclosure

Absolutely. Modern XFS, for example, has checksums on every piece of metadata, and has metadata verifiers to functionally validate every bit of metadata read from and written to disk. So the current version of the XFS on-disk structure is fairly resistant to casual fuzzing. But then fuzzing adapts, and begins to write invalid metadata with a valid checksum, and the arms race continues (as it should, I suppose.)