Here is another question back at you. why do you believe that is a 'fact'?
Not to sound like a dick, but is there a reason you think a neck with a headstock would in fact make it stronger? To my knowledge a headstock is usually thinner than the rest of the neck, so would it not make more logical sense to believe that a headless would be stronger because the tension is on a bigger/thicker piece of wood?
Ibanez RD 707 Basses > Radial Tonebone Bassbone(pedal) >Empress compressor (pedal)>Way Huge Porkloin (pedal)>BBE Sonic Stomp (pedal) >GK MB500>SWR Golight 112 or house PA system