From the RFC:

It uses the server nonce from that challenge, herein called
nonce-prime, and the client nonce value from the response, herein
called cnonce-prime, to construct A1 as follows:

 A1 = H( unq(username) ":" unq(realm) ":" passwd )
 ":" unq(nonce-prime) ":" unq(cnonce-prime)

this is not applied here, which is not using the usernamme and realm in the construction of the A1 value.