Kingston Predator showing up as "External" Drive in Disk Utility, Blocking Boot Camp Install
I was able to add a second PCIe flash card and install Windows directly without the use of Boot Camp Assistant. I was also able to do the same by using Apple Disk Utility to create a free partition on the macOS drive for Windows and install it that way as well. However I opted for the second PCIe flash card to keep things simple and segregated.

Now, when I boot and hold the Control key, I get "Macintosh HD" and "EFI Boot", the later of which is Windows.