But they _are_ writing the firmware that runs most of them and need to understand those devices at a deep level in order to do that, unlike Dell. Dell slaps together hardware and firmware from other vendors with some high level software of their own on top. They don't do the low level firmware and thus don't understand the low level intricacies of their own systems.

No they're not unless I'm mistaken. They're not writing the firmware that runs on the NVMe drives, nor the NICs (they're not even writing the drivers for some of the NICs), etc.

There's a line in the sand that you must cross when it comes to understanding the true nature of the componentry that you're using. At the end of the day, your AMD CPUs may be lying to you, to all of us, but we just don't know it yet.