"While others may attempt to help others and offers their experiences as lessons, Bo knows to keep hawking."
Bo is most, blatant but most posts by people in hte "business" here are some mix of these two things, call them what you will.
My understanding is sub woofer speed and accuracy has mostly to do with damping factor, just like with woofers, but perhaps to an even greater extent.
Cone material can make a difference as well, but proper damping in any case is probably the key.
I have seen at least one well regarded sub maker pitch their proprietary application of what seems to be basic negative feedback applied in the sub's built in amplifier as well.
These few things along of course with overall build quality and design probably would account for a lot of subwoofer characteristics typically described as "speed" I suspect.