Actually he rather carefully pronounces it as "behind the aft nacelle". Given Cumberbatches delivery and the captions/script matching up, chalk it up to random error of the writers.
Could whoever wrote that line be thinking the connecting-dorsal counted as the forward nacelle? From that POV "aft nacelle" makes sense.
Most likely: Writer didn't even realize what they were talking about when they wrote the line.
Given the shape of the forward half of the secondary hull, it's possible that he meant the entire warp drive section of the ship. Which would put life support at the back of the brewery assembly, before the shuttlebay.
Possibly what Marcus was already shooting at when he kept targetting that part of the stardrive both at warp and as Carol hailed him.