With more than 73,000 Borrower Defense to Repayment claims, it would appear that they would be required to sign.
According to the Updated Signature Requirements:
"If the Department has approved a significant number of borrower defense or false certification claims for the institution, or if there are a substantial number of these types of claims under review that, if approved, would result in the potential for significant liability"
https://fsapartners.ed.gov/knowledge-center/library/electronic-announcements/2022-03-23/updated-program-participation-agreement-signature-requirements-entities-exercising-substantial-control-over-non-public-institutions-higher-education