By that logic, we never saw any scenes in the engineering hull, because the only corridor set they had was curved. Sometimes you just have to suspend disbelief and accept that you're watching a television show using the limited number of sets it can afford to build, and use your imagination to gloss over the discrepancy between what they can show and what they intend to convey by it. (For instance, when Starfleet computer console props are used to represent an alien computer center. We're not supposed to believe the technology is actually identical, we're supposed to understand that it's just an approximation of what we're being encouraged to imagine.)
Maybe we didn't. Is that in the engineering hull? You don't know.
My hypothesis is that this is some intergalactic "Acme Corp" run by mysterious aliens who we never meet. This also explains how Starfleet systems can communicate with alien systems with no problem whatsoever.
Kor
Oh, you mean the Intergalactic Department Store.
To be clear, TOS-R clearly didn't establish that empty socket shown on the ship to be the ion pod, albeit it's probably implied. As shown, It's just a hole with the scorching around it. The ship was there for repairs, so it could have been a blown our running light (which is what that feature actually was on the model).
I think you mean "didn't clearly establish," as in it's ambiguous, rather than "clearly didn't establish," as in it's unambiguously not so.
Anyway, it was a shot of a missing component being replaced in the ship, and it was in an episode in which the ion pod had been jettisoned. Stories aren't random; things are included in them for a reason, or not at all. So of course it was meant to be the ion pod. I mean, which is more likely -- that the makers of TOS-R were thinking "Oh, let's just spend thousands of dollars creating a random shot of some people changing a light bulb," or that they were thinking "Wow, now we have the opportunity to finally establish where the ion pod was"? It's not even a question.
Children, children, please. It's pointless to squabble over this, becasue everyone knows the Remastered version doesn't contribute to canon at all and can be completely disregarded.