> You can't break a fundamental assumption without providing it's replacement, and call anyone else stupid.

Sure, within the bounds of what's documented you are right. However tar is going beyond what either standard or Linux guarantee so a lot of bets are off.

The guarantee that tar wants is not given by any FS that recycles inodes and most importantly, tar already completely disregards the file-system locality when network drives are involved.

The actual issue here is that both tar and Linux are just in a tough situation because a) the POSIX spec is problematic b) no alternative API exists today. Something has to give.