does fisheye really give you wide angle on DSLR?

[ville]

I reacently bought Sigma 15mm f/2.8 fisheye for my D30. My inspiration was based very much on luminous landscapes article imagealing: http://www.luminous-landscape.com/reviews/imagealign.shtml

Article said:
A 16mm rectangular fisheye offers one form of solution. When used on a DSLR like one of the above the angle of coverage is reduced to roughly that of a 14mm lens on full-frame 35mm — about 114 degrees. Now we're talking! This puts these cameras back in the wide-angle game.

But here are two pictures that were taken with D30 and the upper one with sigma 15-30 @ 15mm and the lower one taken with Zenitar 16 mm f/2.8 fisheye (note, that the pictures were taken by Finnish photographer Keijo Karvonen, not me)

Angle of view seams pretty much the same in these two pictures allthoug zenitar should produce angle of view 180/1.6= 112,5 and sigmas angle of view should be equivalent to 15*1.6=24mm what is 84.1 degrees.

Am I missing something? Does the zenitars 16mm focal length change something compared to sigmas 15mm?

Thank you for all those who answer, Ville from Finland