Every jump as a base value (BV), and said base value is determined by rotation. If you fall on the element but rotate it, the BV remains intact--you simply get deducted on the grade of execution (GOE), which is maxed out at -3 (plus a -1 fall deduction). So a fully rotated quad with a fall, even after the extra 1-point deduction, is still worth a good 6 points because of its high BV.
However, if you underrotate a jump, the base value itself is lowered. In Jason's case, his quad was a full half-turn short, which means he gets only the BV of a triple. In addition to that, the rules specify that downgraded jumps can only receive negative GOE--double punishment, in other words. All in all, Jason's quad attempt only gave him 2 points.
Granted, Jason's quad deserved at least -2 for the two-foot even if he'd gotten it rotated. What I do have issues with is the cost of the downgrade--why not just give him a BV between a quad toe and triple toe? He did do 3.5 revolutions, not just 3 (and that extra half rotation is far from easy).
I'm also sick of the whole fully-rotated fall thing.

But that how COP works.