It’s not a matter if the factory team interacts with the independant teams. It’s the fact that the factory is actually interested in racing and it makes into the bottom line of their cars.
Chevy is the winningest brand in NASCAR, and that shit sure as hell doesn’t make it to the production line.
As far as BMW not producing the ///M for a year, it’s all part of the ebb and tide. No big deal considering the new 335 is making more power* (and is faster in some respects) than the previous ///M and overall the dynamics of the chasis and suspension will remain, for the most part, the same within the E90 platform.