Why can't I sequence a V3 GIPZ clone with the T7 primer?

It is true that the V2 GIPZ clones possess the binding site for the T7 primer. However, V3 GIPZ clones do NOT. The binding site in V2 GIPZ lies in the cloning linker between the MluI site and the barcode - this area is altered in the V3 GIPZ design.