The information about where the stages are run is literally given to them by ASO. I assume Paul Sherwen is reading from a script when he says everything he does.
As far as knowledge of the sport, seriously? Ever hear Daniel Lloyd commentate? How about Magnus Backstedt? Both are far superior analysts to Sherwen.
I'll give Phil Liggett this one...as long as he's getting the names right, he's very good at calling a sprint. Unfortunately, that makes him far better suited to covering track cycling than road racing. A play-by-play cycling commentator has to be able to draw storylines from content, because road cycling doesn't provide moment-to-moment action. Frankly, Liggett fails in this regard.