> I don’t know what an ISA is

I’m not certain, but I was able to find “income sharing agreement” in this document.

https://www.congress.gov/116/bills/s2114/BILLS-116s2114is.pd...

Edit to add:

Possible related a company he is involved in student loans.

“SoFi, which is now led by ex-Twitter COO Anthony Noto, was founded more than a decade ago to offer ways to secure better financial terms for student loans.”

https://ca.news.yahoo.com/amphtml/sofi-nears-deal-public-mer...