These are dry sump systems, meaning there's very little oil in the engine during operation. Any "excess" oil you put directly in the engine will be pumped into the tank when you start it up. There's really no reason to add oil anywhere other than the oil tank. Adding more than the required amount of oil just makes a mess. It's not like an auto where you risk the oil being churned to foam by the crank.
The instructions tell you to add 2-quarts to the tank and run it up for a few seconds and then top off the tank to the proper level. No need to make it more complicated.