Are the username fields (Authorization section) required in SIP 2.0 to match the data in the from/contact fields?

Question

SIP

The question concerns the Beeline SIP provider.
The provider wants the user-ID and auth-ID to be specified during registration.
They differ in that auth-ID = [email protected]
Translated into technical language. We send the package (after receiving 401 Unauthorized), unnecessary parts are cut out, dog characters are escaped (otherwise the toaster removes them):

REGISTER sip:sip.beeline.ru SIP/2.0
...
To: <sip:user-ID%40sip.beeline.ru>
From: <sip:user-ID%40sip.beeline.ru>;tag=TAG
...
Contact: <sip:user-ID%40IP>
...
Authorization: Digest username="user-ID",realm="sip.beeline.ru",nonce="nonce",uri="sip:sip.beeline.ru",response="responce",algorithm=MD5,cnonce="cnonce",nc=nc,qop=auth
...

And Beeline wants a package:

REGISTER sip:sip.beeline.ru SIP/2.0
...
To: <sip:user-ID%40sip.beeline.ru>
From: <sip:user-ID%40sip.beeline.ru>;tag=TAG
...
Contact: <sip:user-ID%40IP>
...
Authorization: Digest username="user-ID%40sip.beeline.ru",realm="sip.beeline.ru",nonce="nonce",uri="sip:sip.beeline.ru",response="responce",algorithm=MD5,cnonce="cnonce",nc=nc,qop=auth
...

I tried to find this information in the RFC, but could not figure out if the username (in this case, auth-ID) should match the data in the from/contact field (in this case, user-ID)?
UPD: I'm interested in what the RFC thinks about this? To understand, the deviation from the RFC is on our side, on their side, or is it a moot point, and it can be interpreted in different ways.

Answer 1

It may match, but it doesn't have to. It’s just that the provider requires it, there’s nothing strange or new here, in 99% of hardware these are separate fields with the ability to enter different values. username/user-ID can be used to substitute From/Contact/DisplayName, auth is only used for Authorization.

Answer 2

should not match
what is the problem to send as they need?