Unless things have changed, the Summer training options (I'm guessing you're talking about jump school, Airborne Assault, etc...) and how they are selected are at the school/PMS's discretion. I know neither my son or daughters school used the OML to choose who was chosen for those opportunities. My daughter's ROTC program was smaller and they had a surprising number of slots available to them....more than my son's school who had 4-5 times the number of cadets. I know at my son's school, basically the Cadre's favorite buddy-buddy's were able to attend the summer programs. My son was on Ranger Challenge and was the top PT cadet (340 average) for two years and was never chosen to go. My daughter was chosen for a jump school slot her Freshman year and she didn't even ask to go. I have read on this board more than once when cadets posted that PT scores at their school dictated who had 1st shot at those training slots but it obviously varies by school.
Your GPA came into the OML equation when you were vying for a spot in your favorite branch (Infantry, Armor, etc...)