I am afraid you have to create BZ for Fedora, ideally with a reproducer with Fedora (the FDI image is CentOS8 based). You could create such test by converting Fedora LiveCD to PXE and booting that. Or you can reach out to Grub developers too on their mailing list.
There is nothing I can do here, this is very likely a bug in the bootloader. FDI boots fine on other hardware and in VMs.
Workaround: Use iPXE instead.