Grant:
CGX car nut:
Read carefully and one will realize that the manual version never was on table as as a viable option; the design of that rear differential is the clue.
Although AP made it sound like a big deal that the diff needs hydraulic pressure from the PDK pump, it would be easy to add one to work with the e-diff and manual (BMW has been using electronically controlled mechanical diff for ages with manual box - at least since the E46 M3 in 2001). Adding a small pump for the diff would be neither expensive nor very heavy.
I believe that we are reaching similar conclusions: the addition of a hydraulic pump for the differential is not a significant cost or engineering challenge for Porsche. We already know that PDK, at the very least, on paper, offers a performance advantage over the manual, yet Porsche offers this option for "lesser" cars, so this leads one to conclude that Porsche has other motivations. Porsche did realize that the GTS variant of the 997 sold at greater volumes than originally forecasted, and at higher margins. Therefore, based on this, Porsche's management would naturally conclude that a higher margin GT3, with greater market appeal, i.e., with PDK exclusively, would lead to greater sales volumes.