No doubt it will get even better as time goes on and the data improves. Already it's the nearest that I've seen to a reliable service, and it is much easier to use than some others.
There is a feedback form for anything that looks squiffy. So why not give it a try?
I'd suggest double checking anything it suggests by more traditional methods, because automatic route planning for cyclists is supposed to be pretty difficult. But it might suggest a few new ideas, and there should be plenty of scope for tinkering.