Now who is discounting whose canon?
Not discounting canon at all, merely stating that tabletop from Gamesworkshop own stance, holds a lower level of canon then do the Black Library books within their mythos.
I am not stating anything is not canon, I am stating to be aware and recognize varying levels of canon within each mythos.
When debating, and or discussing comparisons between different IP's and or mythos, one should be using examples that do not conflict with higher levels of canon.
Thus if one person presents a argument formulated upon the Warhammer 40k table top as the basis of their presentation, yet the example is in conflict with an example brought forth from the black library books then the warhammer 40k table top example is discounted.
The same goes for the halo mythos when using examples, any example is fine taken from canon material however when a higher level of canon within its mythos contrast a lower level example you go with the higher level display.