the better you get at say wing chun, the more you are restricted by the movement patterns that form part of wing chun, the more difficult it is to fight in a different and more effective way.
I would think that, like other systems, this is only as true as we make it. The movement patterns are the starting point, a way to learn the principles and one possible set of applications. Within the principles are other approaches. I see this a lot in TMA, somewhat less in boxing, and even see it in sports like soccer and basketball. I refer to it as "playing in the grey areas" - the area between the "techniques".