There are 2 specifications at play here:
https://tools.ietf.org/html/rfc7521#section-5.1
https://tools.ietf.org/html/rfc7519#section-4.1.7
Assertion flow should have some “Assertion ID”
and JWT’s can optionally have a JWT ID. They don’t really appear to reference each other explicitly, but it makes sense to use them together.
Assertion ID
A nonce or unique identifier for the assertion. The Assertion ID
may be used by implementations requiring message de-duplication
for one-time use assertions. Any entity that assigns an
identifier MUST ensure that there is negligible probability for
that entity or any other entity to accidentally assign the same
identifier to a different data object.
4.1.7. "jti" (JWT ID) Claim The "jti" (JWT ID) claim provides a unique identifier for the JWT.
The identifier value MUST be assigned in a manner that ensures that
there is a negligible probability that the same value will be
accidentally assigned to a different data object; if the application
uses multiple issuers, collisions MUST be prevented among values
produced by different issuers as well. The "jti" claim can be used
to prevent the JWT from being replayed. The "jti" value is a case-
sensitive string. Use of this claim is OPTIONAL.
It appears MSFT have opted to call their Assertion ID claim nonce instead of jti
