@philip - There’s a little bit more to that second file: “It’s a memory-mapped file, so it’s constantly being written, but is subject to standard file caching.”
However (another warning from Mary TMI St.John), like many under-the-covers" and not-documented-elsewhere tidbits that get shared here, using these files creatively is not officially supported, subject to change at any moment and all the other fine print. And as @philip pointed out, likely to change between firmware versions.
But the Opto Tag Preserve utility is fully supported. So are persistent variables, which are for this purpose exactly, so we need to get THAT fixed for sure, if it’s not already.
Always fun to explore other ways of doing things, though. That’s what we do!