Internal programming.
Better one in the 3* than the 6*, in terms of "contribution"/appearances and probably max. shooting % effectiveness, like 6* have a max of 1 goal 20 shoots as max, and the 3* maybe a 1/5 as a max. so wth 3* is next to the max. and maybe actually is 1/18-12 goals per shoot?,,,,
All in this game, are internal limits and calibrations created from a selection of variables.