That isn't a PG thing; Linux[1] ext3/4 does not actually delete files (or directories) that are still in use. Only the name is removed. The file itself remains until the last open handle to it is closed.
[1] Amongst other OSes
I did read it carefully (and quoted the whole thing for context), but that final line made it seem that it was PG that was responsible for that particular instance of resilience.
Someone who isn't familiar with how ext3/4 handles deletes might, from the comment alone, assume that the same sort of thing would happen on other filesystems.
So the snark does seem out of place and the clarification useful.
Is it really constructive to throw insults[1]? I explained myself above, after all.
[1] I had to look it up to see what it means: https://en.wikipedia.org/wiki/White_knight. Since we aren't in a business context, I can only assume that you think I am female :-)
I hope that eliminating a single drive fault failure mode isn't part of the unfinished business.
Twelve years ago RAID 6 and 60 definitely existed. Battery backed FC arrays of considerable sophistication have existed for far longer. I'm thinking HDS arrays circa 2002 for peak redundancy complexity (before integration reduced parts and physical runtime concerns making the installation environment as important as the technology.)