With Unified Kernel Images, how are custom initrd scenarios (such as multipath boot) addressed?

I was looking at the Fedora change set for 38 and saw this which seems like a neat idea but I was wondering how this affects systems that need custom files to be present in the initrd. One example is booting from a multipath device where the multipath configuration needs to already be present when it goes to setup the root filesystem. I'm sure there are others though.