I assume the stepless aperture is for videographers, and the shift function is for architecture photographers. I do not presume to speak for either audiences, so I'll pass on any further comments.
This is what someone would assume if reading only the specs.
In practice it is different: the range of the aperture control is very small and difficult to adjust. The scale is also very small less then 4mm from f/11 to f/32.
The shift function could only be used with APS-C Cameras (mentioned in the manual). You could only shift vertical and only +/- 6mm. Nothing in between. No scale. No possibility to fix. The disadvantage of the additional moving parts and the possibility dust and humidity getting inside overweights the advantage.
With the Eos R i cannot use it at all, with my former 80d i tried to use the shift but the effect was always to strong.
the reviews you can read just as well as I do?
The reviews of the 15mm Laowa are good examples why i prefer the experience of owners:
"The shift is said to work best on APS-C.
It can be used on 35mm frame, but there is likely to be vignetting. "
John Riley reviews this unique ultra wide-angle 15mm lens with 1:1 Macro reproduction and shift feature.
www.ephotozine.com
I tried it again yesterday and the shift turned a straight line into a S-shaped curve. The quoted statement is simply wrong.