Fractalsponges work, (as incredible and detailed as they are) are in many cases his own interpretation and not accurate to the actual cannon material. His ISD while closer, is still off in all three categories mentioned above.
In the case of the "snub bow" I think at least part of the reason was, they didn't want something dangerously sharp and fragile.
Compare to Saxton's close-up of the Devastator bow:
It would be handy to see exact figures for the Avenger and Devastator models (length, width, width of bridge) and some conversion using all having the same "in-universe length" of 1600m, to tell us how long and wide and "bridge-width" they'd have in-universe.
Then do the same with the FFG Armada ISD model - and we'd know exactly how far out it is compared to the other two.
We know at least that the Devastator model was 91cm long and the Avenger model 259 cm long:
http://www.starwars.com/news/star-wars-mysteries-exacting-executor-measurements
And I've measured the ISD model and got 20.5 cm long, 13.5 cm wide, 3.5 cm bridge width.
Converting to "in-universe figures in metres" - that's 1600m long, 1054m wide, 273m Bridge Width.
Edited by Ironlord