The idea here is that a GM that know their stuff understands that structures are needed to make for a good gaming experience, and hence even if put in a situation that were advertised as pure freeform they would introduce structures strongly corresponding with well established patterns of game design.
So as the ideal system in this case would be the one the GM designed themselves, and in such a system no rule would be in the way. However most GMs don't have the luxury of having time to write, the gift of words to express their insights, and players willing to read trough their homebrew tome. Hence the need to pick an off the shelf system. And it is in this sense I think the best those rules can hope for is to not be in the GMs way. Any that actually is in the GMs way are likely providing a lesser experience for the players than what we would have got if the GM could have reigned free from it.