[Request] TUF B450M-PLUS GAMING - PCIe 4.0 BIOS MOD

BIOS/UEFI Modding BIOS Modding Requests
3

I could just flash the BIOS with version 1804, which should support PCIe 4.0.
But will the processor I use be properly supported?
Why does it not work to mod a current BIOS to do this?