Looks like 7th gear in the PDK is just a cruising gear. 6th gear in manual and PDK are identical ratio (with same final drive) and 7th is just for fuel economy and low noise.

PDK does have some slightly closer ratios (like shifts between 2nd & 3rd gears), but there is no complete realigning of the ratios for pure performance. Top speed will be achieved with 6th gear in the PDK, like a Corvette in 5th

Gear Manual PDK
1st 3.91 3.91
2nd 2.32 2.29
3rd 1.56 1.65
4th 1.28 1.30
5th 1.08 1.08
6th 0.88 0.88
7th ----- 0.62

Final 3.44 3.44

I bet they will save the real benefits of the 7 close ratios for the new GT3 (make new 7th gear close to the former 6th and move all the other ratios closer together)...