Well, I agree with the old time fiddler. When I was a young girl, I remember someone telling me that some fiddler's prefer a flatter bridge to help them with double stops or shuffles, where most violinists prefer a more rounded bridge to aid in articulation and clarity. So, in this instance there may be a slight difference. In most cases though, whether for fiddler or violinist the bridge is rounded according to the shape of the fingerboard. It all depends on who's soing the playing.
Fiddler plays the fiddle.
Violinist plays the Violin. There are some of us who do both. Honestly though, it's not so much what the instrument is called that matters. What matters is how much a part of the musician it becomes. A loving tune from teh heart of a fiddle player speaks more deeply than thought.