At the risk of oversimplifying things...some engines are born with shorter rods than others, and can benefit from a longer one.
THE 225 IS NOT ONE OF THEM...period, end of debate.
The engine is insanely oversquare with not nearly enough piston surface area to adequately work the crank without massive amounts of leverage. The longer rod decreases this leverage, reducing angularity in the early stages of the power stroke...exactly where it needs it the most.
When someone finally offers a cross flow, overhead cam cylinder head for a the Slant that is capable of supporting 10,000 RPM, there will be some merit to a longer than stock rod in the 225. Until then, it is pure idiocy perpetrated by people who have too many fingers on their hands