Okay, I'm wrong, but it was a guess. Even so, you didn't say "spec is in the sig" or something like that, like most members would say. This would have indicated that the sig is up to date. Although in a hindsight the processor should have been a indicator that the sig is up to date, as the processor is only 2 years old. I will take the hit, since your issue was near similar to mine and I responded hastily with a possible solution since the said solution fixed it for me. So... Sorry about that.
Perhaps you may have you figured out what an iGPU is? Just in case, It is an Integrated GPU. Sometimes known as onboard GPU.
Hopefully you will get your issue resolved.
I would have thought the BGRT is stored in the firmware, which I thought that it would survive a drive formatting.
I learned something new today.