As someone who's had a couple of miscarriages, I certainly agree that the "abortion" tag is not at all applicable in the case of an irrevocable, involuntary termination of a pregnancy for physical reasons outside the control of the pregnant person.
I suppose I'd have to look at the story in question to see if the tag was used to indicate a miscarriage caused by abuse or some other factor that wouldn't be outside the control of one of the parties. I do know that in the case of an impending miscarriage if surgical methods are used to facilitate matters, it is referred to as an abortion.
I'll defer to the admins as to the need for a miscarriage tag, but if you can link me the story in question, I'll check for the appropriateness of the abortion link.