They share an almost identical excerpt:
Questions related to the definition and nuance of meaning of a word or phrase
This tag is for questions related to definitions and nuances of meaning of a word or phrase.
I agree that technically word-meaning is a subset of meaning, and that reasonably by synoymizing word-meaning to meaning browsing questions / answers tagged word-meaning would end up showing also questions / answers tagged meaning, but as it stands browsing questions tagged meaning won't show questions tagged word-meaning, which should instead. Another point is: is it really important to distinguish between the meaning of a word or a, say, phrase when looking up questions / answers? Shouldn't the purpose of the word-meaning tag be to group questions about the meaning of a word under meaning in general? Wouldn't it be more convenient expecially when browsing questions?
Also, quoting the related FAQ on Meta.SE: