There is absolutely nothing wrong with these procedures, balancing a single or twin cylinder
vertical motor of any type is hit and miss/stab in the dark as far as flywheel weight is concerned.
Blokes like Magnetoman could spend 20 years calculating what he thinks is right to find that
in the real world the bike had intolerable vibes at xxxx RPM.
Yes, it’s trial and error. Anyone can see how, in many individual cases, it can be better than the prescriptive factory advice.