I am astonished that anyone could think that Froome has in any way a 'perfect style'; he just looks so ungainly on a bike! In fact his style is perhaps the worst-looking in the entire peloton.
I also see that the usual suspects have come along to shout down any suggestion that pedalling style is any way important, referring to those experimental studies that failed to find a link between style and gross efficiency. Without going through that debate again, I think that it is significant that despite what the 'experts' say, many riders are convinced that a 'good' style helps them to delay the onset of fatigue and so forth and most professionals do have a very 'smooth' pedalling style. This makes me suspect that the 'experts', who after all not that long ago were telling everyone that elevated levels of blood lactate 'caused' fatigue, are missing something.
I recently read the following paper:
Fatigue is a brain-derived emotion that regulates the exercise behavior to ensure the protection of whole body homeostasis
http://www.frontiersin.org/striated_muscle_physiology/10.3389/fphys.2012.00082/abstract
This paper essentially argues that fatigue is not a physical state at all, rather a neural 'Central Governor' acting on multiple cues, triggers a feeling of fatigue in order to maintain homeostasis and prevent damage. In reality, in a trained person at least, the body is actually capable of much higher levels of work, if only this 'Central Governor' could somehow be over-ridden. (Which is exactly what drugs like amphetamine and caffeine do.)
Relating this to the old 'pedalling efficiency / style debate, it strikes me that one factor that might contribute to the 'emotion' of fatigue is how well a rider is able to maintain a 'smooth', 'coordinated' pedalling style. Studies show that, when riding at the limit, the style of even the best rider tends to break down. It seems quite possible that this break-down in style would create neuro-muscular cues that the 'Central Governor' would, along with multiple other cues, interpret as signalling the onset of a state where homeostasis is threatened. In turn, it would follow that the longer a rider is able to feel that they are pedalling in a smooth and coordinated manner, the longer they would be able to suppress these cues.
In short, you feel fatigued in part because of a failure in the ability to maintain a smooth and highly coordinated pedalling style, not because this directly influences gross efficiency but because of the influence this has on the functioning of the 'Central Governor'
Doubtless the 'experts' would cling to the old view that it is the fatigue that is the limiting factor here and the breakdown in style is just a symptom of this. However, as that paper above argues, fatigue as a genuine physical state may only occur at a level of work way beyond the point where the rider actually feels fatigued.