Okay, I figured it out. When you revised your guide (by crossing out the stuff about IE) you also left out to replace both boot.wim and setup.exe from the windows 10 ISO.
So close, and yet so far! I followed the instructions. When my computer boots to the UEFI USB 2.0 I get the Windows 10 version of the setup screen, but when I click "install now" I get the following:
Any ideas?