You hit on my favorite topic-
rod length vs stroke-
The DA is the only engine which mentions it .
The increased rod length is an idea accepted by some race tuners and rejected by others but the advantage -as mentioned --is that IF the cumbustion which starts at -say 15 degrees of crank rotation BTDC- the amount that the piston will rise is lessened -also th piston spends more time at the top -before starting down.
It then moves relatively faster at mid stroke.--
All of this can assist in the gas flow INTO the crankcase-on a two stroke.
Another advantage is that more compression can be used - giving more torque.
Why? well the problem that can exist in some engine designs is that the combustion chamber -if squeezed after the flame has started-will autocombust at the far side of the chamber - and this is detonation - Not pre ignition -not Pre detonation(?) a term oft heard.