Bzzzt! Wrong! You don't have to move an inch for the front hubs to re-lock after you change direction. It's a function of the axles rotating, nothing more. The axles are able to rotate within the hubs without the wheels moving at all. If the rear wheels spin, then this happens without you moving an inch.
The problem is that the rear wheel(s) must actually rotate at the same time since there is no center diff. For the front shafts to rotate, the rear shafts must also rotate. This results in only the rear wheels doing work for the (maximum of) 1 rotation of the driveline. On the X with 31" tires, the vehicle would travel about 8 feet assuming it takes a full rotation of the front axle within the hub to complete the dis/re-engagement process (it's probably less) and that the rear tires actually have sufficient traction to move you the entire 8' while the front end isn't helping (in which case, no problem).
If the rear end doesn't have sufficient traction, well, they'll spin one full revolution (or less) in place while the front end re-engages, then you'll be in 4WD again. Problem is the rear wheels may have dug in deeper or slid sidways in the process, and THAT is where the brief dis/re-engagement manifests itself as a problem. Also, if the wheelspin is rapid, the shock placed on the hubs as they re-engage can damage them.

Make sense?
Brent