It boots the 64-bit PE because of a detected UEFI Bios. You might be able to turn on traditional bios in the settings. Otherwise, on your PXE rep, delete the x64 PE and copy and rename the 32 bit WinPE to match the x64 version name.
That worked - I had to actually disable all EFI boot devices in the Storage --> Boot Order section.
I initially disabled only the USB drive in that section, but it seemed to still boot to EFI.