That's the thing. There needs to be room to penalize jumps that have multiple errors -- underrotation and also other errors.
At a certain point a really really badly failed attempt will end up not getting penalized for everything that was wrong with it. But just 3 levels of GOE reduction is not sufficient to distinguish between jumps with varying degrees of underrotation and no other errors, jumps that are fully rotated with errors, and jumps that are underrotated and also have other serious and/or multiple errors.
If anything that's recognizable as a triple attempt is to start with the base mark of the fully rotated triple, then judges need to have the option to distinguish between a fully rotated jump with mostly good technique that ends in a fall, a moderately cheated jump that otherwise looks good, and a badly cheated jump that's also badly telegraphed or has an incorrect takeoff, etc., and also results in a fall, step out, or two-foot landing.
Mid-point base value for jumps cheated 90-180 degrees, with GOEs up to 0 allowed especially in combinations with only one cheat, and down to -3 for other errors, is one way to do it.
Full base value with negative GOEs down to, say, -5 would be another way to handle it. The really disastrous attempts might deserve more like -6 or -7, but you have to draw the line somewhere. -3 is too generous for those failures compared with lesser or fewer errors.