X-Drive Staggered Question (any new info?)

[dawg1]

Researching the internet, I've seen multiple posts stating x-drive tire sizes must be within 1% of each other. I can't really find the source of this and wondered if any new information has come to light.

I also found this by another poster:

"The xDrive system has a calibration and correct function at startup that looks at the wheel speeds and determines the correct rotational allowance for the tire setup. As of 2015, I've seen some technical documentation that indicates it will consider up a 2% spread as valid."

and "The BMW awd system is not always locked like some other manufactures"...

On the newer models (say '14 and up), is there really a calibration system or is the 1% rule still the guideline? I have access to some good tires that are 2.3% different and am trying to be certain they cannot be used on x-drive.