I discovered the same as the OP today and I have to agree with him that it's ridiculous behaviour. If a non-privileged user copies another user's files using
-p I would expect it to retain modification dates, group ownership
if the user was in that group, but certainly not user ownership
unless setprivgrp -g CHOWN is set, which in my case, it isn't!
So I end up with a crazy situation where I can copy privileged files/dirs into my home directory (for example)... and then I can't get rid of them, modify them or anything! What a silly thing to have to bother the system admins to fix (luckily I'm one of them, but...).
ETA: I can't see how to change this behaviour using
setprivgrp? Do you mean using
-g CHOWN? That would increase a particular user's capability to chown files... to emulate the more sensible behaviour of other Unix we would need to
reduce such a capability to prevent it from happening to copied files. Am I missing something?