Well, wow uses the word ‘race’ which means something different in the real world so first you’d need to define that. Once you’ve defined race then just see if it aligns with what a species is, if BEs and NEs are different species then no it’s not cannibalism.
If Blizz asked me to define cannibalism for them for lore I’d say it was “the consumption of a humanoid by a humanoid”.
That should cover most everything that could be “questionable” since I belieeeve everything that is ‘real world human like’ (murlocs, kobolds) is classified as a humanoid.