That is similar in principle to the Tecumseh method, mechanised a bit. If you hammer it very hard or for any length of time, you'll deform the end of the crankshaft so it's difficult to put the nut back on. Worse, it gives a considerable hiding to the bottom crankshaft thrust bearing, and it has the potential to bend the crankpin slightly so the two main bearings are no longer colinear. If it is a horizontal crankshaft engine with two ballraces for main bearings, you'll probably trash the one at the PTO end.
In other words, I think there is a good reason that manufacturers do not recommend this method.
