Well, that is quite true, but let's say you are flying an ILS or VOR approach; what will be your primary guidance? You could just "use everything you have" but life soon gets too cluttered.
I am not sure that is completely true with glass - if that is the point you were seeking to make.
With both the G1000 and Avidyne clearly you will be closely monitoring the PFD during the approach - whatever type it is.
Both work in much the same way, except with the Avidyne the plate is painted underneath the rose on the PFD which is a very good idea.
In both cases you are going to have the procedure painted on the moving map on the MFD. Combine this with terrain and not only can you ensure the approach is proceeding in accordance with the procedure but as you descend below then some of the surrounding terrain will be painted in yellow and then red on the PFD.
I think it is possible for the pilot to monitor both screens.