That's the weird thing. It DOES detect it just fine, and I get into Windows and use it no problem, even on the same boot as when it beeped. Further, this was happening on the Integrated GPU too. I like to think there are no connectivity problems with the internal GPU on the CPU die, right? 😉
I'm pretty confident that it's caused by the motherboard's display detection algorithm. If my monitor is powered off, the Intel GPU would act like it was completely disconnected. If I was in Windows, you'd hear the hardware removed beep, just from pressing the power button on my display. That doesn't happen on my Nvidia card because it physically knows it's connected and is always there. But I think the same mechanism (hardware disconnect upon monitor power off) is triggering the BIOS to assume I have no display connected to the computer at all, just because the monitor is powered off.
Is there any way we can get a BIOS update that allows me to ignore having no displays connected? Kind of like I have a CPU fan plugged into the fan controller but the motherboard freaks out, until you specifically ignore the missing fan header. That would be nice and stop it from beeping at me because it booted up before the monitor did.