But if it does work, then overall mortgage rates will marginally decline. Better information will lead to better choices, so mortgages will become less risky overall. Some people will suffer, but keep in mind that when those people oppose this, they are saying "I want to hide material information from the people with whom I do business; if they knew the truth about me, I would get a worse deal." That's fraud.
Yes, there will be false positives. And it's easier to visualize being the victim of one of those than it is to visualize the tiny collective improvement in human welfare that tends to result from better decisions.
I would be interested in an argument that applies in this specific case, but doesn't apply to the general class of rough but useful heuristics, like "Kids with bad grades who drive recklessly are probably less responsible than 40-year-old moms who drive minivans, even though there is some C-student with a red car who is safer than some particular 40-year-old minivan-driving mom."