I think the point about cutting is valid in the sense that it limits how big a bat could be. Standard clefts I think are limited to 70 or 75 mm in raw form, while oversized ones are 80-85mm at the apex with correspondingly bigger edges. So that limits the maximum size possible in terms of edges/spines for most bats.
Pretty sure than GN definitely use oversize clefts on some models (at least in the heavy weights) as their extreme models in the UK (or the Australian Colossus) can be quite massive. If they cut their own, would not be much hassle to use a special cleft for a pro like David Warner. Then you can add all the other aspects like lighter density etc.
As for the optical illusion, i think that is also true particularly with the Tempo or the Distinction. I have a fairly heavy tempo (2.14 or so) with spine around 68mm. On its own it looks very massive, and I think the same applies when you see it in pictures by itself. The small edges and large spine lead to an exaggerated effect in terms of how big it is. Whereas if you compared it to other bats at a similar or slightly heavier weight with the standard large edge profile you can see its not all that massive either (at least in this case).