I would call that a bug, though it would be rare in practice because you likely wouldn't use metric dims and imperial calculation units at the same time. It must have been a glitch between the dimension standard saved with the project and the default calculation units of a fresh copy of 12 (US version I presume). But it's still weird because calc units are saved with the project too.
Even though it's a rare bug, it's a little unsettling to have multiple prefs affecting displayed values in a non-obvious way.