Usually, in programming languages, the first couple or so parameters for methods and functions are, in the very low level, stored in registers (as long as they fit). This is a very easy optimization that we can do in the first-time code, as it is not really intrusive and does not affect code readability or flexibility; and, in the end of the project, parameters reordering might be just way too dangerous.
However, does this apply to the Unity Player? I could try to benchmark it, but I think that some “solid” information would also be good to know.