I don't think it's bunk but it really depends on terms of reference. If someone just wants an instrument to make a noise, well...yeah. A piece of driftwood will do that...or cardboard...or concrete. All it proves is the importance of rigidity.
If someone wants to talk about the influence of structural rigidity, mass, density and dampening on timbre then I think there's plenty of room for discussion. But there's also a lot of misinformation out there as well...like the influence of species.
At the end of the day, I'm aware that a number of manufacturers like Dingwall and Ernie Ball (and maybe PRS) just weigh a piece of wood from a desired species and if it's within acceptable range, it goes into an instrument. Their instruments, on the whole, are remarkably consistent in sound given how variable wood can be in its characteristics.