When making an AIO, it's possible to collect different Windows releases in the same WIM file.
Every image is saved as a separate instance, and each image can have a different CU applied. But the ISO folder surrounding the install.wim is shared. Therefore you can't have multiple versions of DU, since there is only one ISO folder.
You should skip installing DU for an AIO project. DU is entirely optional, all it does is force Setup to check and download new updates before it begins installing Windows. I have seen more problems from having DU around, compared to its benefits.