I do both in camera negs and enlarged dupes (done on an enlarger). I don't specifically indicate they are one or the other. However I show a bit of edge so someone who knows the difference can see it. I don't think it is something to be concerned about on a title card. I do generally indicate it in places where more information is appropriate, like flickr or in bios.
What I do have a problem with is someone being dishonest. Making an enlarged or digital neg and then presenting it as in camera. It would be easy for me to do that. I would merely need to use a film holder to hold duplicating film under the enlarger. I don't do that.
My enlarged negs are generally larger than my in camera negs. So the value of enlarging them is obvious. My in camera negs are mostly 8x10 and my enlarged negs are 9.5x12
Dennis