The everything wedge shaped reasoning falls apart the second that Ton-falks, Lancer Frigates, Gozanti's, Carracks, Nebulon B's and B2s etc come about though. Not every Imperial Warship is wedge shaped.
Except the part where all the things you just listed are lame(except the Gozanti's which ARE wedge shaped).
Yes, not every Imperial warship is wedge shaped. Just every well designed Imperial warship.