THis.
Since all references to Common" and other Languages come from Settings, it is obviously setting dependant if "COmmon" is the same Language.
As I expect the huge mess that are 1st to 3rd party books never got a coherent ruling about it, I would say:
"All Settings that are on the same world and made by the same publisher mean the same thing if the say common, all others: YMMV".
I mean it should be obvious that 2 totally isolated human societies on different worlds that have no common origin except being human do not use the same lingua france. ^^