I don't think it's just a matter of conflicting evidence, but of conflicting meta-accounts of what is reliable evidence. For its time, Chronicle was marketed as a source of truth - everything in it should be taken as is and would not be changed. Later, when it was changed to be the perspective of the Titans because Blizzard realized that marketing Chronicle in the way they did was a bad idea, it became a fallible source of information which was subject to change; however, people are still holding on to the original intent behind Chronicle. I agree that we're at a point where we should just accept retcons are going to happen, if not just because Shadowlands was predicated on a slough of retcons to the Warcraft 3 story and the Legion overall, but it's understandable that people are going to have difficulties letting go, especially since some books are being retconned within the same year of their publication (for instance, Chronicle released in 2016 and Calia's resurrection by the Light was within about a year, which directly contradicted it). We're in a situation where we have some people who are legitimately confused, which is understandable, and people who want to outright rejecting the changes out of frustration.
Something we also need to keep in mind is how much old novels, like the War of the Ancients trilogy, damaged the online discourse. Even today, over a decade since we've found out how powerful the Titans are, you will still occasionally find people appealing to quotes from the War of the Ancients to try and convey the power of an Old God (i.e.: the quotes from Krasus). Considering that Chronicle was supposed to be a much more reliable source of truth, we're probably going to see confusion far into the future. I wouldn't be surprised if in two or three expansions there were still ongoing questions about changes from Chronicle and that the very question of necromancy was brought up again in the future.
Note: Obviously, this isn't me saying "people should reject the change", just that Blizzard really needs to start getting their ducks in a row before publishing a deluge of contradicting sources that fragment the story and introduce confusion.
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Magic that uses "death" as its source of power.
Is this ambiguous? Yes.
Will this ever be elaborated on? Maybe, people can say if this has been elaborated on before.
Chronicle outlined each cosmic force as being a source of the power (such as death) and a type of magic used to express that power (such as necromancy). This is no longer canonical for necromancy, but it may still be canonical for other types of magic that were given the same relation to a cosmic force (such as fel magic's relation to disorder). This is possibly subject to change, although I would say it's likely this solely affects death (and maybe life and nature because Eonar and Golganneth had nature-related powers).