It won’t help students from low SES families in general. What will likely be the case is that the subset of students from low SES families who successfully navigate the current application process for highly selective schools is the same subset who can handle the new process. This subset is likely defined as:
a. Those attending high schools which are have a significant high performing student cohort. At such high schools, the “college admissions culture” that exists in the form of support from counselors, teachers, and high performing peer students helps remind high performing students to stay on track with PSAT / SAT / ACT / recommendations / FAFSA / CSS Profile / essays / deadlines. In contrast, an outlier high performing student in a predominantly low performing high school may not get any attention or support for college aspirations beyond the local community college or commuter university.
b. Those whose biological parents are married, as opposed to divorced. Divorced parents may be uncooperative with financial aid forms or paying the expected family contribution. Students with such uncooperative divorced parents may be shut out financially from the highly selective financial aid based on need only colleges.
But even this subset is far more students than the highly selective colleges “need” to get some SES diversity. They do not “need” or want too many, since that would consume too much of the financial aid budget; they also need enough students paying list price (top 2-3% income families) to balance the budgets (and various other favored admission groups like big donor relation, legacy, celebrity, athletes in sports associated with high SES, etc. tend to come from high income families).