Arlon, that looks like a fun setup.
At low magnifications, this is the perfect way to use an enlarger lens -- short focus distance on the back of the lens.
A bellows lens at this same focal length would indeed be designed "reversed", with short focus distance on the front of the lens.
On the other hand, a bellows lens designed for the same fractional magnification we're seeing here would be designed like the enlarger lens, with short focus distance on the back of the lens.
But because of the longer extension implied by bellows, the bellows lens would also have a longer focal length. A good example is the 135 mm Olympus bellows lens (
here), optimum magnification range 0-0.5X.
That longer focal length causes more of a "telephoto" perspective, in contrast to the more "wideangle" perspective that the enlarger lens will give. That's maybe good, maybe bad, depending on what effect you're looking for. It also reduces the angular coverage of the lens, making it easier for the designer to get flat field and uniform resolution corner to corner. The 135 mm Olympus is an awesome lens, with something like 4X higher resolution at the sensor plane than my DSLR can capture. (See bottom few images in
this article.) But it's not very handy for shooting hand-held in the field.
--Rik