*ASRock do NOT recommend updating this BIOS . . . B450M Pro4

[RZap]

Bought a B450M Pro4 motherboard, support page states "*ASRock do NOT recommend updating this BIOS if Pinnacle, Raven, Summit or Bristol Ridge CPU is being used on your system" for bios version 3.9--which is what it shipped with. It won't let me flash to an earlier version. I bought the board to use with a Ryzen 5 2600. Why is it not recommended? Why ship with a bios not recommended for anything earlier than the 3000 series?