I didn't see any discussion on meta for this tag and there seemed to be a few questions that this tag could be beneficial for. As a synonym, I would perhaps suggest
this is the question to which i added this tag.
I would say there is a need.
I agree that both the phrases are used for the same thing, so the solution to that is to make them synonyms of each other.
What is not a solution is to arbitrarily select one, and banish the other.
Both the phrases are used equally. Google Scholar gives approx 17,500 results for vector conflation and about 19,000 results for map matching.
OSM's wiki mentions both the words.
So, I'll argue that both the phrases are well known, and we should keep both the tags, after making them synonyms of each other.
This is not a term that I have come across previously, so personally I did not see a need for the tag. However, one has already been created so that point is now moot.
I recommend that you or someone now creates a tag wiki entry for it so we know when it should be used.