DX12 will give potentially better multithreading which may help people with AMD .
The current situation is the limit is the one core that is running the main thread and there are not enough other processes to use more than half a dozen other cores effectively. The game uses about 6 cores, totally trashing one of them and partially (typically 25% to 50%) using the rest. Hence currently there is little benefit going past 6 to 8 cores and no real benefit to hyperthreading.
This is not unusual in gaming.
It will also mean RT and DLSS are possible though nothing has been said about Asobo working on either of them at present.