"Engineering" isn't limited to one location on the Enterprise.
Indeed, it would be quite possible and relatively easy to fit something like six Engineering sets in the secondary hull, e.g. one at each end of a trio of longitudal shafts ("warp cores") that would tie to each other with those prominent angled tubes on the shaft walls. And each location could be symmetrically expanded so that the visible set would only represent the portside or starboard half of the whole. That would cover most of the variation in the (factually single) set seen during the run of the show, while still leaving much of the engineering hull empty.
Clearly, the one interpretation that is not
plausible is that Engineering would consist only of that single set. It's said to be a maze where one could hide basically indefinitely, after all.