I find this part very interesting.
Because you have "All-solid" instruments where the backs and sides are (apparently) made from the same solid wood as the top. And these are generally considered to have the best sound. But the sides and back are the same (?) as the top, not harder.
And then you have the "Solid-top" instruments, where the top is solid, but the sides and back are laminate (harder, less resonance). These instruments are generally less expensive than a similar quality "All Solid" instrument.
So according to your reasoning, the "Solid tops" should be better at projecting sound than the generally more expensive "All-Solids"?
I think the small size of Ukuleles tends to muddy the works somewhat. Typically in the guitar world, the top is more flexible, usually being Spruce or Cedar with sides and back made from a harder, more "reflective" wood like Rosewood. You don't want the back to vibrate as it would essentially "subtract" from the available sound waves and you'd lose some volume out of the back of the instrument and lost in your body.
Each laminate is different, but I don't think you can generalize that all laminates are harder or less resonant. If it was a rosewood veneer over a softer core wood, the result would be worse, not better than solid wood. Plus you have bracing to contend with. You want a rigid body but still want the top to vibrate as freely as possible. This is easier with small instruments than it is with large spans of wood like you see in a guitar.
Similar to MGM's recent experiment where listeners couldn't really identify solid vs. laminate by sound, the same holds true for guitars. A solid top/laminate back and sides can sound just as good as an all solid wood. Some classical guitar makers do this on purpose to create the sound they're looking for. One builder lines the body (i.e. "laminates" it) with Cypress, to brighten the sound of his instruments, most likely for the tastes of Flamenco players who want a more "lively" sound.
Ukes and Mountain Dulcimers are two instruments where top wood choice seems to defy logic. Perhaps it's simply because the small size and limited vibration of the top doesn't significantly add to the overall "sound" of the instrument, and harder woods sound better in this case. That would explain MGM's results where people typically couldn't guess laminate vs. solid tops, and in some cases their choice for the best sound came from one of the cheapest instruments.
It seems to boil down to a matter of taste, and what sounds good to "you."