No, I'm not aware of any using N/O and N/C, but I don't get into it much these days. I agree it could be ambiguous, depends what you consider normal, maybe electrical guys have a clear convention.This discussion is, of course, all about the markings and (per the OP) how they can/could be confusing.
I don't think we have yet seen a case of any non-electronic stat, or any associated wiring diagram, using "NO"/"NC" terminology - they seem to invariably use "C"/"1"/"2" or "1"/"2"/"3". Are you aware of any (non-electronic) stats or diagram that use "NO"/"NC"?
As Eric has demonstrated in the other current thread, and as may be what the OP in this thread has discovered, at least some electronic stats seem to be different, in that they do use "NO"/"NC" descriptors - but, as Eric has suggested, this probably relates to the state of the contacts when the stat is not powered - leaving one to have to work out how "NO"/"NC" correspond to the usual "C"/"1"/"2"/"3". Indeed, as has been said, Eric's one has a jumper which enables one to change that relationship!
Kind Regards, John
Edit: too slow at typing again, probably due to greater verbosity!
If in doubt you can always set it to say 50deg C on the bench, so it will definitely be calling, and check what it's doing with a multimeter.