He didn't see the ship, he briefly saw a schematic of some kind, a corridor and perhaps a piece of the underside of the saucer.
He saw the overall shape, and he did help design and build the NX class. Not as much as Trip or his father, but still, he has enough knowledge to look at that schematic and think, "Interesting shape. I wonder why. Okay, that's there, that's there, I don't know what the hell that is, and there's actually a head directly adjacent to the bridge, which is a
great idea. Okay, we're moving on, I'll think on what I've seen some more, later. Maybe this shape is worth playing with...."