The willingness to sustain massive losses and press on could also be why the Swordies win
Ermattungsstratgie could be part of the reason and an appreciation of it did color the Confederation naval doctrine I suggested to Hans while he was writing GT:SW.
However, there's a great difference between throwing legions at Pyrrhus of Epirus or human waves at panzers and combat between starships and that difference is economics. Infinite missile boats only work when you can build, maintain, and man them in infinite numbers.