Here's my input on the topic.
I personally haven't bought one of the Vision Challengers, so keep in mind my view is from the outside looking in.
Technically speaking, assuming all of the Challengers came with the two sets of drivers in sync, then the sound would be prototypical. If they were to come with the drivers in sync, but with the sounds out of sync, that would not be prototypical. For those who are arguing that in-sync drivers on an articulated wouldn't stay in sync for long (because of wheelslip, vibrations, etc), then to model the physical drivers going out of sync on these engines, you are asking for something that simply isn't easily do-able on a model train with traction tires.
I'm certain that as soon as folks who sent their engines in get them back, some will be whining about the fact that they didn't rotate one of the driver sets to match the sound set. Like Bryant said above, Lionel will not touch the wheels. My suggestion is, if you want articulated sounds so badly, and also want the drivers out of sync, take the risk and send the engine into Lionel and get the new sound set, and then (carefully) adjust the drivers yourself, although you will void the warranty by doing this. There's a tutorial on YouTube!
I hate bashing on manufacturers and on other forum members, and it appears that this is exactly what this thread has devolved into. There is no such thing as perfection. Many people in this hobby worry too much.
Now go run some trains.