Not sure what you mean by "compromised." But simply put, it's not a Haldex system. Haldex is compromised in a lot of ways in part of just the way you can't turn off the traction control system so it will always interfere. The electronic braking stability system will always kick in any why this system tends to eat rear brake pads. Compare this against the Ford Focus RS (GSK Twinster) or the VW 4Motion systems (new Mk8 Golf R and Audi RS3) if you want to remove the SH-AWD system. The Toyota JKEKT system just lacks the torque vectoring of those systems and instead relies on Torsen (if so equipped) LSD's to handle L/R grip which will retain a more 'natural' handling car vs the artificial torque vectoring overdrive which can feel electronic. It does incorporate the overdrive gear which Cammisa says is the best bandaid for the FWD based system to get the rear to rotate on power. But it is not the same as the Subaru (differential) or Mitsu (electronic clutch but no rear overdrive gear) or any differential or torque converter based system. Good on you for not blindly trusting the forum though, far too many times people just accept the easy answer like no one said the system isn't static, so it must be... Simply makes no sense to build it the way they did if that was the goal. Best resource all in once place I've found is this, but of course look for other answers. Unfortunately with any full time clutch based AWD system though, the clutchpack is an ingrained wear part and probably will need replacing more than a few times during the car's life BUT also note how many cars you see these systems on, so they can be reliable to a point.Maybe I can rephrase. I'm just trying to understand if the GR-Four system will feel more like Haldex or a true full time AWD. Maybe the rear wheels will sense loss of grip fast enough that I couldn't even tell it was FWD based. I want a natural AWD feeling car on track, similar to how a subaru or evo might feel. I always strayed away from the Golf R, because of Haldex and the CTR because of FWD. The GRC is an incredible car, make no mistake, but I don't want a compromised AWD system.
As for pages 2-3 and throughout this thread, you've kept repeating your beliefs that the GR-four system is closely related to SH-AWD and certainly not a true full time AWD. Your reasoning makes complete sense to me, but I haven't read any other thread or article reach a similar conclusion. Even the in depth thread over at the GRY forum posted by OP doesn't mention it. Not to say you're wrong, but I usually like to hear from more than one forum member before considering something as factual.
However, in regards to driver feedback? Based upon the GR Yaris owners, it's a lot more of a driver's car than any Haldex. Put it on the same arena as the reviews for the TLX Type-S, Audi RS3/Mk8 Golf R, Ford Focus RS and now a bunch of others (but mainly used in more SUV applications). Just look up GKN Twinster as most of the designs are adopting their architecture. In general you'll see the feedback for their systems is very good with the main complaint being more about the torque vectoring aspect as a gimmick. But if you're looking for a RWD feeling car? None of these FWD based systems is it, it's the BMW xDrive and other RWD based systems that you're looking for.