After reading SQLite's page on their public domain approach they seem to go through great lengths to make sure it stays public domain.

https://sqlite.org/copyright.html

Including having their closed contributors sign affidavits and stored in a physical location. This may be what OP is referring to.

Compare that with an MIT license with no "hardening" like affidavits so that it's easy to mutate to another license type, I can see their point.

Interesting stuff since I never knew this "public domain" approach before!