The Nebula class filming model was quite different from the study model used for BoBW. If any of the other designs had been given fully-fledged filming models, they would probably have looked different as well. There were two entirely different rationales for the Wolf 359 ships and the DS9 kitbashes, the main fact being that the former models were not built specifically for BoBW, but were originally 'study models' built by a contracted professional model maker to show that components of the Galaxy class could be rearranged to create new ship designs in an effort to convince the producers to budget for new filming models instead of constantly reusing the TOS movie models. They were used for BoBW because they were available. The DS9 kitbashes, on the other hand, were hastily-built concoctions by members of the production staff, out of multiple types of kits without regard for scale or era, and were never meant to be scrutinized up close.