...
To be fair, doing the 3 years IS completing that portion of the obligation. Should one desire to come out of SELRES, they met their commitment. If the Navy wants more, just put it in the contract.
At year 5 , it doesn't matter what your points are. You have an 8 year minimum obligation, of which 3 years SELRES and the rest however you want it to be. Stay in SELRES...go IRR...doesn't matter. If you choose IRR, they will not require you to get points. At the same time, the 27 points thing doesn't matter; they will keep you on the books with 0 points per year until your 8 year obligation is up.
After your 8 years, they no longer need you on the books, so they look at your yearly points after that. If you are failing to get the 27 points AFTER your MSO, they eventually get around to discharging you.
Just keep in mind, that should you do this (0 points) and change your mind and decide to pursue retirement, those years will be "bad years" and too many of those will screw you later. If you even remotely desire to obtain retirement, you need to get 50 (35+15) points at every opportunity.