I have recently seen some methods which have a boolean parameter called simulate, specifically in some code for minecraftforge by RWTema as well as code in the RF API. What is the point of this parameter, if I don't want the code to actually transfer items/energy/etc why would I call the function. Is there something I am missing about the parameter that could be useful or is it sort an extra feature that most people won't ever use?

I can sort of see how that is useful, but there are already functions to get the amount of energy stored which don't have a simulate parameter. Is it likely that RWTema implemented it in his minecraftforge patch because he uses the RF API for his mod and is use to the concept of simulating transfer of objects?

Possibly. It is often used to determine what would happen without actually executing that action. e.g. determine how much energy could be extracted without actually extracting it, or determining how much fluid can be inserted into a container without actually inserting it.

So could that be used to transfer over only what can be transferred and not lose anything?