Is there a structural difference between the FG-335 and FG-3

I have a FG-335, but I haven't seen a FG-340 in person. I have to assume, for manufacturing purposes, that they use the same bracing for all models of the same size, they only changes being the outer layers of the plywood and possibly some minor visual differences.  These are mass produced guitars, efficiency is more important than fine tuning for a particular tone.  But you never know!!

Spec-wise, the FG-335 and FG-340 are the same, except for the 3 piece back.  You'd think the 3 piece back would make a minor difference in tone, but I think it's mostly visual, looking to capture some of the Martin D-35 market.

But there are differences between some models.  I've had a couple of FG-345's and they seemed to have deeper tone than a FG-335.  Maybe it was just the rosewood vs. mahogany plywood?

There are some internal FG-335 pics here.  yamahavintagefg.boards.net/thread/566/1980-yamaha-335-neck-reset

I've taken a few pictures of the 3 plies of the sides at the end pin hole, and when removing the neck for a neck reset.  In all cases the inner wood is some kind of light colored wood.  So, I assume it is some kind of filler wood. So, you'd think there would be no difference in sound and weight between a plywood mahogany or rosewood model, but there certainly is.  The rosewood models are much heavier than the mahogany models.  And the mahogany models are a bit drier, and the rosewood models have more overtones.  Maybe not as much as solid wood guitars, but the difference is there.