Let's imagine that all the Bitcoin devs were arrested by a tyrannical government or bought by an evil mega-corp and forced to change a fundamental aspect of Bitcoin.
Open source doesn't work like that. The code is OSS and anyone is able to modify it and fork it. Current developers (be it Core, XT or whatever) have no more control of it than anyone else.
In the end it's always the network that decides. The control is decentralized and collective.
Only way that some goverment could have it's way is if majority of network accepted it or stubbornly kept running a client that is under govt. control. But at any time they would be free to choose otherwise.
You are right of course... the point of this exercise is to determine what features users consider fundamental to Bitcoin's nature. If that is clear enough, it could prevent forks that endanger those features. Or in the case of technical issues where outcomes are more uncertain, it tells developers what user priorities are.