I would definitely agree, for several reasons…
There is a threshold point that the Germans should not cross in how many territories they occupy, because then they will become more vulnerable to Allied aircrafts. Not going for Cherbourg means more concentrated AA.
The Allies waste quite a lot of time just moving down to Cherbourg. It is nice if your forces hold a little longer in Cherbourg, but seeing as how it takes the Allies 6 movements or so to trek down to Cherbourg and up to St. Lo, holding the city for one additional turn is not a huge difference in the delay of those forces. The Americans land 0 tanks until later in the game, so the force that takes Cherbourg will be predominently 1 movement units unless they take it late game.
Fighters are an obvious threat to any german units which decide to travel across the whole map.
And finally, if the Allies actually put a lot of units towards Cherbourg to take it very early (a fast start could be somewhat harmful to the Axis) then Germany easily has the offensive tank power to take advantage of that large Cherbourg invasion force by harrassing and destroying isolated British units and landing Allied units.
A viable option I see is keeping a mobile tank force between St. Lo and Cherbourg, so you could threaten a late reclaiming off Cherbourg. If the Allies compensate by leaving a large enough force down there, you can easily divert the tanks to St. Lo.