Moreover, in the entirety of DS9, we never really saw a ship constructed during or for the war. All the vessels appearing on screen had registries lower than the known prewar Voyager. So perhaps we should argue the exact opposite of the above: perhaps it is impossible with 24th century technology to build a starship in anything shorter than four years?
The USS San Paulo's registry was higher then Voyagers by a difference of nearly 1,000.
Given the number of ships we saw take part a vast majority of them were unnamed. Of the ones that were named the bulk would be of older designs the we know for sure predate the Defiant. Most of the possibly newer craft such as the Akiras, Sabres, Steamrunners and more modern vessels such as the Galaxies and Nebulas we have no idea what their registries were to judge when they might have been built.