Where did you read this because this is not true... Sense of scale, with regard to loudspeakers, is an illusion created both visually and by what you think you are hearing. There is no quantifiable or identifiable characteristic for "scale"... That stated, speakers that have wide dispersion, thus creating a large soundstage, in combination with good bass extension and midbass punch create the illusion of a large scale. Driver size has nothing to do with this, at all....
I have listened to pro-gear with 15" woofers designed for high efficiency - at the sacrifice of bass and poor directivity, sound significantly "smaller" than a pair of well designed satellite speakers in combination with a properly integrated subwoofer.
Baltic Birch has nothing in common with the bamboo material we use. Besides being much less expensive, baltic birch is full of voids and is not a cross ply. Birch is also less dense with much shorter fibers. Bamboo has very long fibers which dramatically reduce / absorb resonance, it is stiffer, environmentally friendly and truly sustainable as it is the fastest growing plant in the world.
I would choose MDF over baltic birch for a speaker cabinet as MDF is less resonant. Baltic Birch has the advantage of being much lighter though, so there can be considerable cost savings involved for larger speakers due to the reduced weight for shipping.