I don't know about that. From my private email conversations with MSI motherboard team they seemed very… incompetent. They didn't know what the options they added to their firmware did and they didn't seem to understand how UEFI Secure Boot works (they thought it also works for non-UEFI OSes, somehow).
I have an MSI Z370 board. It does not support x8/x4/x4 PCIe bifurcation in BIOS despite chipset support, and using the latest BIOS it fails to POST with an Intel Arc GPU in the first slot. This latter issue is maybe defensible as Z370 doesn't technically have support for Arc, but I've read that 300 series boards from other vendors work fine, so I'm going to hold it against MSI anyways.