If there's a wins floor in the league (and I'll never join another world without one), owners sometimes have to promote guys earlier than they would like. Without such a rule, it's not tanking if an owner doesn't bring guys up before he's ready to compete. If he's not playing people horribly out of position, starting 0% P, trading away good older ML players for non-prospects, etc., he's not tanking. Without a wins floor it makes no long-term sense to promote players just to win 60 games instead of 45.
Sometimes when you post looking for a certain answer, you don't get it.