How could they have possibly missed this issue with Intel HD Graphics drivers? I might understand if this was some obscure hardware that few ever heard of and even fewer actually use, but an Intel HD Graphics driver.?

We all wish MS would do a better job with their updates. And -hopefully- you'll delay installing it on all your other PCs for a while to give them a chance to fix these bugs and the all bugs yet to be found. But you still were brave to try it so soon, even on just one PC. Microsoft rolls these updates out in 'waves' so not surprising v2004 was only offered to you on one PC. I wish Microsoft would make a better effort at resolving issues with their major Windows 10 upgrades before they release them on the user base (and then tell us, 'by the way you probably shouldn't update.'). I'm now running the latest Nvidia Driver and everything is working fine (it even resolved an annoyance I had with the fact the Dell BIOS Splash screen was displaying in the wrong aspect ratio).

That resolved the Intel issue by replacing the GPU (disabled the Intel GPU in Device manager, for whatever reason there doesn't appear to be a way to disable the onboard GPU chip in BIOS). I had a Dell OEM version of a Nvidia GT 720 laying around that I had replaced with a more substantial Graphics Card in my Dell XPS8700 PC so I installed it in the 3647 (I had never paid any attention to the fact the 3647 actually had a couple of PCI expansion slots until today). Actually the only PC (of 4) that has offered to update to 2004 through the Windows Update and Security control panel was the Inspiron 3647 so I took a chance to see what would happen.

Intel 4600 graphics card db9 connector