When I read "conflict" I think, somebody has a question about a conflict.
When I read "conflict-aversion" I think, somebody is very keen (for whatever reason) to avoid conflict.
So the two terms do not seem to mean the same thing. Some people's excessive conflict-aversion may even avoid conflict in a sense, but can itself cause or complicate interpersonal problems.
Example: a woman asking the hypothetical question "how can I address the extreme emotional coldness of my spouse without endangering the future of my marriage -- I want to absolutely avoid any sort of confrontation/argument over this issue" might well use the tag "conflict-aversion" rather than "conflict." Same with someone asking "how can I deal with an extremely aggressive boss without creating any problem in the workplace?"
It is also notable that you found both tags were used over 60 times. Wouldn't merging the 2 tags make more sense if one of them were being used much more often than the other? In fact I found a few instances where both tags were used on the same question.
Update: as noted by OP @NVZ in comments, one tag (conflict-aversion) has been used 120 times and the other only 60. However, 60 is not like 5 @NVZ. Given the option of "conflicts" and "conflict-aversion" around 35% users are choosing "conflicts" (60% chose "aversion" and 5% used both) and that is significant.
Short term solution: there is a subtle difference between the 2 tags and both have been used over 60 times here, so there seems not enough reason to merge them right now: but we can review a few months later.