Right, having looked for more solid info on DX12 tiers and what is what, I am still clueless. Some are saying that MS have lowered the DX12_3 spec because nVidia paid them to do it

Some are saying that GCN has been downgraded but there is no actual facts on GCN being fully supportive of all DX12 components (it should with AMD being in the Xbone) or Maxwell being fully supportive of all DX12 components, so gawd knows.
http://semiaccurate.com/forums/showthread.php?p=230750#post230750
Some good comments in there but doesn't really answer anything. Worth a read for those interested
I hope TX is fully DX12 compliant but if not, that will be a downer.