i don't have a backup of the system i just upgraded (which is a rarely used laptop), but on my desktop i have a full mirror on a secondary disk, which i didn't update after the last upgrade yet, and here i see that /lib64 _was_ a symlink ... but it pointed to /lib!? i won't exclude the possibility that this was the result of a manual fixup after something went wrong with a previous upgrade. also, the upgrade on the desktop went through cleanly, maybe because it was already much more current and therefore had a newer dpkg (1.22.6 instead of 1.22.1), or because the fs state was actually different (which we won't be able to determine).
with the manual invocation, dpkg removed the previous /lib64 just fine, so this seems to be (or have been) a bug in file conflict logic? i'll also note that it was "suboptimal" that dpkg noticed that it cannot install the new package only after removing the old one, thus leaving the system entirely without /lib64. this would have been mildly painful if i didn't have a root mc running in another terminal, which made this a 10-second fix. but that's for another report ...
