From park up through to completion and packing up,10 minutes would be extremely quick for even the smallest of houses, not saying that it can't be done though! 
Actually Helen on a standard semi of say...12 windows in total, providing access is straightforward and the windows are in good condition, even on a stand alone account it can be done in under 10 minutes - from pulling up to driving away - no problem.
I have a few like that, they are a breeze, and the quality of finish if top notch, and of course that also includes all of the frames and doors too.
But there is most certainly a skill involved in being able to clean quickly, no newbie reading this should think that its a total doddle and that anyone can do it.
As in the original post on this subject, the guy in question has been using WFP for many month and he is absolutely crap at it by the sounds of it
Ian