“Even if the college scrupulously protects each divorced parent’s finances from the other, it is probably not difficult for either parent to reverse engineer the other parent’s finances using his/her own finances and the financial aid offer that the student gets.”
That cannot happen. Why? Because the documentation (eg. an IRA Form 1040) uploaded by parents and students is static; from the Student Portal, they can only read or view it as a PDF or jpeg. Meanwhile, the data from the 1040 (for example) is extracted from the PDF, etc., placed into a data file, and then sent to each of the financial aid offices at the applicant’s schools.