Where does failure come one play?
GT4 was a fantastic deal because Porsche wasn’t sure it would sell and they mispriced it. They sold plenty and won’t repeat the cheap price mistake. If offered as PDK they could have sold many many more but would have kills GTS sales.
911R was the best looking 911 in modern history, the first GTx without a wing and sold to Porsche VIPs to create an artificial halo around it. It was oversubscribed times over.
GT3 touring is what Porsche enthousiasts really want minus the PDK. It will sell relatively well but would sell multiple times over is it had PDK. If offered as PDK it would have cannibalized GTS sales, their very high margin product.
Regular GT3 is sold as manual and PDK. Clearly PDK outsells manuals.
Again, clearly, not being offered as manal is clearly not an issue, on the contrary.