Now if I as DM have already decided that the villain has taken the shortest route... then why should a PC who is looking for a shorter route succeed?
If you, as a DM, have taken that decision and are intent on retaining the authority to make that decision, that's a playstyle choice. As far as I can tell, this thread is about exploring alternatives to that playstyle choice.
I would assume it is important to the narrative thus why should it suddenly change?
The question in the thread, though, is whose narrative is it at any given point?
My other question is what is the limit? I mean does the DM try his hardest to accomodate each and every idea that someone comes up with to change the narrative as long as it isn't contradicting an established fact? Does the DM only get narrative control when the PC's don't want it? What if two PC's want the narrative to go in a different direction...who wins out?
It tends not to work like that. Groups tend to move from a dictatorship to a democracy. Stuff gets talked about, ideas get thrown into the mix. Some happen, some don't. Stuff gets resolved, between friends, concessions get made, deals get done, like the way it does if two people want to see a different movie.
See my problems isn't in the giving of narrative control to players, however in a game where there is no structure set up to account for it (in other words, something to make it a limited resource) it becomes what I would call the "uber power".
Really? Is this from experience? If so, our experiences differ massively. In my experience, as I said in a previous post, players don't do this.
I don't think balance in games like FATE come from 'compels' or limits to narrative power in the way you seem to describe. For example, in FATE, if I want to be a jerk I can write really dull aspects like 'I am aweseme at everything' and 'I win'. FATE requires players to write nuanced aspects with both positive and negative connotations, but nothing in FATE forces you to. But if you don't you short-change yourself of all the fun. FATE players know this.
In my experience, players who want narrative control also understand how to use it to make the game more fun. They don't use it for a lame instant counterspell for the evil curse, they use it to say the curse can be broken by the mystical hermit on Dragon Peak who was rumoured to have died 200 years ago.
Clearly if you've already decided 'how the narrative goes' then this is a problem. But this isn't about 'good' or 'bad' or 'should' or 'shouldn't'. It's to say it need not be a problem, if it's how you aim to play.