Microsoft has undertaken a part of responsibility of providing driver support through their update channel, as announced once in a keynote, in order to improve reliability and security, pushing a new way of driver certification process.
That's why contacting the vendor, as you mentioned, either Broadcom or Apple, returns with a negative answer, that Microsoft is the one eligible for driver support and hence the vendor to contact when problems occur. Vendors are directly responsible for
their faulty drivers or softwares, when they provide them directly on their websites, which is here not the case!
In other words, Microsoft pushed an "MS-Certified" driver and therefore MS is the first one to blame on certifying such faulty drivers. Also MS should have contacted the vendors about the faulty drivers released, in order to fix them.
Contacting vendors reveals that the drivers pushed by Microsoft are "Microsoft Drivers" and they are as hardware vendors not directly responsible for faulty drivers.
So it is true, MS does not write drivers, but they did certify them as safe, reliable and working! MS should now take responsibility to report this issue to the vendors, namely Broadcom or Apple.
Das ist so die richtige Aussage, oder? ;)