I think it's accepted that UC/DC are still both only partly canon, in that, where they contradict the main games (not including RE1, RE1C of course, as REmake is clearly the current canon take on that story) they aren't canon, but where they fill in blanks, they are.
BIO1 has no actual canon in any version and is almost entirely open to interpretation, rather than "what you see is what you get." Except for what's stipulated in later material. Arguably neither does BIO2, as all four scenarios are canon in that game and the actual order is outlined in later material. BIO3 is the same to a lesser extent, only the ending has been stipulated but all of the multiple choice elements are untouched and open to interpretation.