I don't know how you worked out your maths
, I did a bit more maths just so we have something solid to argue over rather than "it looks too big" / "no it doesn't"...
Measured distances on the image (had to discard a lot due to cropping & low contrast); then compared these against the actual dimensions of the airplane (had to discard a few more, I didn't know lengths of wing + horiz stab leading + trailing edges). Some variance in the scales is ensured by perspective, low resolution, and probably my own mistakes.
Pixels per metre for the 744:
3.89 Between wingtips
3.90 Shadow of wingspan
3.87 Nose - tail
3.60 Nose - tip of vertical stabiliser (as the crow flies)
3.70 Between inner engines (centre axis)
3.80 Between outer engines (centre axis)
Pixels per metre for the 388:
4.39 Between wingtips
4.09 Nose - tail
3.75 Nose - tip of vertical stabiliser (as the crow flies)
3.89 Between inner engines (centre axis)
4.10 Between outer engines (centre axis)
4.12 Horizontal length of wing / wingbox join
So the 388 is definitely shown with more pixels per metre than the 744. In other words, it's unrealistically large.
Hope that helps!