Here's the result of five miniutes on google... no idea whether there are specifics involved which do not show up here.
The supp regs are here:
Under Superstock it says the following:
10. Wheels:
● Wheels must remain as originally produced by the manufacturer at the time of
sale into the dealer/distributor network for the homologated machine.
● No Carbon fibre composite wheels are allowed, only aluminum alloys wheels
are permitted to be used.
● The speedometer drive may be removed and replaced with a spacer.
● If the original design included a cushion drive for the rear wheel, it must remain as
originally produced for the homologated Machine.
● No modifications of the wheel-axles or any fixing and mounting points for front and
rear brake caliper are authorised.
● Spacers can be modified. Modifications to keep spacers in place are permitted.
● Wheel diameter and rim width must remain as originally homologated.
On the BMW page here:
The S 1000 RR has now been made even sharper and more precisely geared towards pure performance on race tracks or country roads. For everyone demanding the maximum from themselves and their bike.
www.bmwmotorcycles.com
It says:
"The M package sharpens the sporty profile of the RR. Exclusive Light White/M Motorsport paint is only included in this package and gives the motorcycle a powerful look. The package includes: M Sport seat for optimum support on the hunt for crucial milliseconds.
Weight-optimized M Carbon wheels with M graphics for maximum riding dynamics. Or the alternatively available M forged wheels. In addition, the M footrest system and the black fuel filler cap."
So from that incredibly brief check it would appear that the team used the optional carbon wheels even though they are specifically disallowed and there is an approved OE aluminium wheel for the model. Pretty black and white, not sure what their beef is?
If it's as a result of a protest by a competitor, that may well be because they are annoyed at the advantage gained by the other, or feel that they might gain an advantage by the protest, but also it could be genuine concern that they should not have their rider racing in a pack at 300kmh with bikes which are shod with wheels which have been specifically disallowed because of a perceived risk of catastrophic failure without warning. Why the organisers have been letting them run like that is indeed the question. It would be interesting to hear from anyone over there closer to the facts than us.