SBI Grouping, can someone explain it to me
 

Sorry if this has been covered before, I went to the SBI website and while I understand some of the grouping, some don't seem to have guidelines?? How can you have boats in the same groups with different HP and motors if its suppose to be a Production 2 class?? Some have 525efi, 600hp, and 509ci, is the class based on the boat and not motors?? I am not picking on this particular group, just using them as an example being the name "Production 2" ?? Production 1 is even more difference

Thanks