This is an old feature, to make some migrations of way older versions and incompatible caches possible. I assume / hope that no one is running with this of an old cache any more? And, I believe even if you did, it would have wrapped by now, such that this option is no longer needed.
Let me know if you still rely on this option, if not, I would like to kill it, and the cache code, for v9.0.0. — leif
