The driver is the H bridge circuit, thus, the motors share the driver. Optimally there should be two H bridges, one for each motor. This is not likely to be the primary cause for the issue, only a contributor, especially if there really was a bad batch of motors.
There is no need to explain an H bridge to myself or the group as it is irrelevant and more information than is necessary. This is unless you would simply like to exhibit your knowledge on the subject. As well, it is the standard method for driving a DC motor in two directions and braking... If you asked someone that knew a little about driving DC motors how the wheel was driving them, they would undoubtedly state that it was using an H bridge of some type.
I have no explanation as to why the Logitech wheels do not exhibit this same behavior as frequently. They do however have issues with the mosfets and motors on occasion. (people have pages set up explaining the procedures for their replacement) I would need to take my G27 apart in order to look and see how it is configured. However, it is quite possible that the gearing is such that no matter how the motor is inserted, it's poles are aligned. If they were not, the cogging would be far less apparent.
As for the bad batch of motors or some other cause... I do not know the reason for the failures. I can only make statements regarding what I have personally seen and based on the knowledge I have of the issue. Motors should be aligned when directly coupled, it's a given. As well, they should be driven from isolated sources when paralleled.
How many CSR (not elite) or other current single motor Fanatec wheels have you read about that have motor failures? Motors like these are purchased by the hundreds or thousands. It's not as though there were 20 bad ones in a batch. Thus, it stands to reason that some of these bad motors should have ended up in wheels other than the Elite and CSW as well. I have yet to read about any of these having similar issues.
Lastly, I don't need to prove anything... It's not my product. There is an issue, undoubtedly, and it seems rather wide spread. If indeed this is a bad batch of motors, then hopefully the new ones will fix the issue.
It would not be maintained indefinitely. You did read what I posted before, correct? Where I stated that it would probably not stay aligned? Sorry, I can't really tell where you are coming from here...