Could equally well be buggy EDID. It's like manufacturers simply don't care about following specs as long as it works on whatever the current version of Windows is. If that means writing a piss poor driver which requires all sorts of hacks to “work” then so be it, or something....

Example: ASUS USB-N11 wireless adapters have the USB fields for “manufacturer ID” and “device ID” reversed! EDID info is like BIOS info in that it is often completely and utterly untrustworthy.

... Just you wait until we'll all have with EFI: it is typically even more buggy!