A fisheye can capture a wider scene than a rectilinear lens, so in that sense it can give you more total field of view. But once you “defish” it, you’re remapping a curved projection onto a flat image, and that has tradeoffs.

You can reduce the fisheye look, but you can’t fully remove the underlying projection geometry. Like flattening a globe into a map, some distortion has to remain somewhere. Typically the edges get stretched, and objects near the sides can look as if you were viewing them more head-on than you really were. In practice, that means some of the extra width is gained at the cost of edge accuracy and natural rendering.

So yes, a fisheye may capture wider coverage than a rectilinear wide-angle lens, but defishing does not create a perfect ultra-wide rectilinear result for free. If you want the widest possible coverage and can accept edge distortion/stretching, fisheye plus software correction can be worthwhile. If you want a more natural-looking image across the frame, a rectilinear wide-angle option is usually the better choice.