I've always thought this too. In fact, due to this, I think it's fun to assume that the majority of that wing structure is devoted to the functioning of the warp drive on the D-7 and not just the pylons and the nacelles.
Yes, considering Klingon technology is assumed to be not as advanced as Federation technology, it would be quite a scandal if their warp drive components would actually take up less space.
Thus, the Klingon warp engines are most likely only the warp coils, while the nacelles of the Enterprise
also include the matter-antimatter reactors and the antimatter pods. Would be fun to visualize how much of the Klingon Battlecruiser's engineering hull would need to be a part of their warp drive to match the volume taken up by the nacelles of the Enterprise
Designwise it's fun to assign a jet intake design, very common in the UK in the 1950's, to the Klingon (or - in Hornblower context - Spanish) antagonists, while we may be looking at a Soviet jet intake design (e.g.: Mig-21) that has been adopted for the warp nacelles of the TOS Enterprise
(don't dare to imagine the rec room discussions Pavel Chekov might have had with Scotty regarding such a design influence