So many sempervivum have similar traits that once a tag is lost it should always be referred to as a NOID so that mis-labeled plants aren't traded and sold. Unfortunately that's one thing about sempervivum - they're
very difficult to ID. Clint, I don't think Twit was getting nitpicky, he's just being honest and trying not to confuse the issue.
Examples of how similar calcareum and tectorum look
