Do you have any references for this? Because that is truly scary. I've heard of isolated instances of the manufacturer-installed crapware silently trying to update the BIOS in the background, failing, and resulting in bricked machines upon the next boot, but that wasn't Microsoft's doing.

including security risks

That is BS, unless you are talking about things like user-hostile "secure" boot, which are firmly in the area of "do not want" anyway.