Draw back in this sentence is used literally, not figuratively, and it means 'pull back'. I'm still not sure what the discussion point is, though.
I think you're looking into this far too much 源尘小道人. There's nothing about the quote that mentions limiting how far you draw the arrow back, which would necessary for it to make the metaphor you described.
The sentence is probably literal, as Su Ki mentioned, in which case it's just describing basic physics. If it's a metaphor we'd need to see the context to figure out what it's implying.
I heard some proverbs like the statement you said. That might indicate if you want to jump higher, you must squat down lower to brew more energy for the jump (figuratively)
Iam not so good in english, but I think that this sentences could have many meaning, depending of the person itself who is reading it.
what I see is that more our background is stronger and more we can reach a higher sucess, it could be studies , wealth or family support.
Just like the golden section,everything has its best point. But if you beyond this perfect point,something might get bad.'draw back' in the sentence means that if you want to shoot an arrow as far as you image,you'd better bend the bow into a point which is best for it rather than make it as possible as you can. For instance,when you are rowing a boat,it is not the more strength you use,the faster the boat move.