Until recently, I would have said that this discrepancy would almost certainly be because of the way Brown takes into account home equity. According to this survey: https://www.thecollegesolution.com/wp-content/uploads/2021/06/Home-Equity-Listings.xlsx
“July 2020: Per discussion with Matt Davis Fin Aid counselor at Brown, Brown uses 100% of equity, but encourages families to appeal. He mentioned that Brown can adjust the assessment rate on asset 2-5%, though the standard for home equity is 3.6% of home equity.”
Many similar institutions cap home equity at a multiplier of household income—most commonly 2x income, though 1.2x income is also common— and then use an assessment rate of 5%.
HOWEVER, Brown has excluded equity in the primary family residence as of 2022-23:
“The University will eliminate the consideration of a family’s home equity in their primary residence as an asset when calculating a student’s available financial resources.”
With this change, I don’t know why Brown’s NPC would be comparatively higher presently. It could be that their on-line NPC hasn’t been adjusted accordingly.
I have seen cases where FA offices admit that their NPCs provide inaccurate estimates based on home equity Mt. Holyoke is one such institution. Their NPC shows lower need-based aid numbers than what actual aid amounts would usually end up being.
You could run the Brown NPC with and without home equity entries to determine the sensitivity of their calcs to that.