Oh! I could be wrong but I think I know what's going on. If you download/use the official ISO, it contains both Home & Pro and it's too big for FAT32, therefore Rufus changes to NTFS automatically.
Ahhh that makes sense.
So that means we would have to turn off Secure Boot.
C.K.
There are 11 editions of Windows in the ISO not just Home and Pro, but even with only Pro the size of the install.wim exceeds the 4GiB limit for creating the normal FAT32 USB Media.
Rufus always used a the weird UEFI-NTFS trick to get around this issue, it is nothing new.
The bottom line is that Rufus does not create the correct USB installation media like it is done with MCT.
MS should make the insider ISO with the compressed install.esd instead of the install.wim and that would fit just fine in the normal FAT32 Installation USB media and there would be no need for Rufus or any other weird utility to create the Installation media.
It only takes a little extra extra step effort for MS to distribute the ISO in the right format, and that would eliminate all these issues.