The saying “what happens in theory not in practice” suggests that while an idea or principle may be theoretically sound, it may not work as effectively or be applicable in the real world.
In other words, you could have all the qualification in the world, but aren’t able to put it into practice and fail at the task in hand.
Likewise, the matter of fudging, to make one sound better than they are, will sooner or later catch up with you, when it’s proven your not at the level, the task requires.