After a bit of research, I’m forced by facts (NS records can be cached for an undetermined time) to see what you’re saying. Thank you for teaching me.

The workings are, of course, a bit more complicated than what either of us have said (here’s a taste), but there is a situation as you describe, where separating the registrar from the name servers, and the name servers from the domain, could save the domain from going down.

If a registrar goes out of business, ICANN transfers the domain(s) to another registrar.

If a name server business fails, you change name servers through your registrar.

You can’t really fix registrar services in your name server, nor name server problems through your registrar. (Unless, of course, your registrar is also your name server.)