What is the priority for something being canon? The impression (in descending order) I've gotten is:
>rulebooks
>models
>WH+ animations
>white dwarf
>warhamner community
>black library
>video games

With two special exceptions
>something is canon until information from an equal or higher priority bracket supercedes it (Wraithbone, Terminus Decree, female Custodes)
>something can become more resistant to being superceded by being cited in a higher priority bracket after a large amount of community attention (Captain Titus, Blood Ravens, Uftak Blackhawk)