Threadripper 3000 Pre-Launch Megathread

[MazeFrame]

that the socket wasn’t “compatible” with pcie 4.0

I doubt it is the socket, more the tracelayout on the mobo. The “repeaters” on X570 are much more numerous than on X370.

Also:

Ryzen 3000 & Navi Megathread | Level One Techs

More likely, AMD looked at how some X399 boards were just barely in spec, some needing fan kits or recieving upgrades/overhauls when 2nd Gen TR was released.
From that, it is not a bad decision to save themself from “so, my new computer caught fire”-videos and just push a new platform.