Glenn Highway goes from Anchorage to Glennallen. Richardson runs from (I think technically Big Delta) Fairbanks to Valdez. The Glenn and Richardson highways intersect at Glennallen.
The Matanuska Glacier is on the Glenn....which I think is the glacier in question.
Unless one drove from Anchorage to Valdez on the Glenn/Richardson and took the same return, one would not cover the entire span twice. Only the Glennallen - Valdez portion....that portion does not include the view of the Matanuska glacier.
Need to carefully check the Whittier - Valdez ferry schedule to ensure which run you're taking: the fast ferry or the milk run. Don't know that it makes much difference price-wise, but will have a big time impact.