No, because there's hardly a person out there who spins a carrom ball more than their off-spinner; maybe Mendis (could argue that it is his stock ball). Simply because you are relying on your fingers only, rather than the use of the wrist - too much of that and it makes the ball too easy to pick.
Stock ball doesn't mean traditional off-spinner, it just means the ball that you are going to bowl the majority of the time. It has to be consistent and dangerous to succeed in longer formats, which we gear our spinners towards.
Stock ball is different for lots of bowlers - Damien Fleming's was an out-swinger, just because he bowled fast-medium doesn't mean it was the same as Paul Reiffel's.