The parable of the lock and key

Reading "An Introduction to Radical Constructivism" by Ernst Von Glasersfled got me thinking about lots of stuff especially when i came across the lock and key metaphor used to explain the difference between radical constructivism and metaphysical realism and the whole idea of "fit" vs "match". FOr the purpose of this blog, i'll dwell on the lock and eky here and sometime down the road tackle the "matching" perspective of the metaphysical realist. he parable describes the world as a burglar faced with a challenge of opening a lock for which he doesn't have a key. He goes on a step further to say that locks could be opened by different keys thanks to locksmiths and burglars and he relates this to humanity being burglars faced with this challenge of unlocking the truth of the world and doing so in various ways ( different experiences).
Some criticize von Glasersfeld for his use of this metaphor as a subtle way of promoting radical constructivism as a "higher" philosophical doctrine than metaphysical realism as well as the obvious reason of laying out the concepts of radical constructivism. But i'll rather refain for that but attack his metaphor for its obvious flaw; the same one the Vico quote fell victim to. LIke vico he talks of real truth but tries to elude it by saying we don't know of it till we expereince it. Humans might not come to know and understand the world in its entirety but that doesn't change that fact that there's a world out there outside our experiences. The burglar trying to open a lock with a duplicate key nows he's its not the original; even if he succeeds in opening it, he is still away he's wasn't the key made with that lock.
So my problem with radical constructivism is this exactly;our experiences are definitely our keys to unlocking to the mysteries of the world but to suggest that the truth of the world is only what we know it is is absurd like someone who thinks his lock can't be picked by a burglar with the right tools.