Originally Posted by Jon-Lars
Consider what happens when the bike accelerates and decelerates.
The battery's momentum is applied to the structure in the direction of that acceleration. You are side loading those threads, with the length of the shaft acting as a lever.
The cut threads are notch points that focus the force, and the base plate attachment gives the lever a fulcrum point.
If what you described were even remotely true, rubber and woven hold-down straps would have to be magic.
The battery is in a pocket. There is a friction component keeping the battery located within that pocket. The ONLY thing the bolts have to do is keep downward pressure on the battery and it ain't going anywhere--same as straps.
Rocking the battery exerts a lifting force and only the tiniest of bending forces. Those bending loads are negligible until long after the battery has translated enough to leave the tray. It's not going anywhere.
My biggest worry in that installation would be engine vibration being transmitted directly into the dangling lead plates in the battery. That's a sure-fire way to destroy a battery.