Is it common that board manufacturers downgrading with revisions like Gigabyte?!

[redzo]

I don't think that's the case. I believe it's wiser to isolate both chips. If one chip physically fails, you've got back-up. I think that a design like that might defeat the purpose of a dual bios feature.

Also, gigabyte does not market rev 3.0 and 2.0 of GA-B85M-D2V as being dual bios capable, only rev 1.1. You can't blame them for being honest.