Have posted this one on Resources and Tools for IT Professionals | TechNet as well.
Have asked Asus whether their technical support could check on this and see whether they could reproduce it and then contact Microsoft developers. Endusers have no entries and can contact 1st level of customer support. Obviously this is a few steps further. Asus might have direct contacts with Microsoft, or Intel, so the could update their BIOS accordingly.
They still suggested to contact Microsoft. This I won't do, for given reasons: I will not get in contact with the developers, which I can understand, but there is even no way to communicate by mail.
Probably this matter will not be solved ('old' Windows 7)...
Also it is a bit difficult to reproduce, because: who has 2x 4TB drives, still empty, in order to simply give it a try..?
And lastly, the group of users who has such drives and wants to put in RAID0 is very tiny, why spending resources on this..?
Is it IRST, is it Windows, is it the BIOS?