he didn't meant the opposite... altho Nvidia could support Mantle : AMD meant it like that (unlike Cuda/PhysX)
he meant he has nV cards(no AMD) so no mantle
and FX-GMC is right : "no AMD is no Mantle" read it like "i have no AMD /gpu/ is no Mantle possibility"
again unless nV support it ... which would be unlikely for them to help popularize a new API made by their concurent
dx11 was developed with close ties to amd so is that soley an amd API(application programming interface)... nope.... mantle is another API like opengl... im sure i'll be corrected if im wrong...
the level is different iirc DX and OpenGL are alike they work on the same level afaik mantle is closer to the core function, but true they are all API, also DX might be a AMD API but nV adopted it because of M$ now if nV will adopt Mantle, which they will not because of some obvious reasons (who said "money" ? ), Mantle could overtake DX as the new standard API because of the evident performances increases and efficiency, ofc DX could still exist but only for other things unrelated to what Mantle is in charge. (i am not correcting you tho )
edit: i will post some result once i am back in the red (not financial status ofc)