Was Cancellara (and his team) going for the fastest possible time when he raced? No, of course not. Hence, I don't understand the argument here.Fabian's fastest time was 2013 on a 254.5km course. 20 minutes slower than today on a 259.7km course...with a chicane into one of the fastest segments on the course.
I can keep going, but won't. Res ipsa loquitur
PS. The Arenberg chicane contributed less than 0.1kph to the race average speed.