In SSO fallback, getAccessTokenMSAL() returns a different result than Office.auth.getAccessToken()

[CBullen2]

URL of sample

Office-Add-in-NodeJS-SSO

Describe the bug

In the sample for SSO falling back to MSAL, the getAccessToken() function in ssoAuthES6.js does essentially:

if (useSSO) {
    return Office.auth.getAccessToken();
} else {
    return getAccessTokenMSAL();
}

The first using Office.auth.getAccessToken will return a JWT containing the user Id details (that then needs to be converted to a Graph access token using OBO flow on the server), but when falling back to getAccessTokenMSAL, the returned JWT is a full MS Graph access token that can be used directly in the add-in (scp has all the Graph rights). Trying to use the JWT returned from MSAL blindly for the OBO flows fails the documented validation rules for a userId JWT (iss starts with https://login.microsoftonline.com, scp=access_as_user etc). Shouldn't both calls return the same thing - i.e. the msal response.idToken rather than response.accessToken?

To Reproduce

1. Edit the code in authRedirect.js to return the full response back to the calling add-in

JSON.stringify({ status: "success", result: response.accessToken, accountId: response.account.homeAccountId, response:response })

2. Put a breakpoint in the add-in message handler code to see what's in the full response object
3. Note that there's an idToken as well as an accessToken
4. Note that when decoded, the idToken matches the result of Office.auth.getAccessToken
5. Note that the accessToken can be used as the auth token in a rest call to Graph directly, without needing an OBO flow.

Expected behavior

If getAccessTokenMSAL() is supposed to reproduce Office.auth.getAccessToken(), I expected to get the idToken from the MSAL function call.

Environment

• Platform [PC desktop, Mac, iOS, Office Online]: PC desktop
• Host [Excel, Word, PowerPoint, etc.]: Excel
• Office version number: version 2405
• Operating System: Windows 11
• Browser (if using Office Online): ______

Additional context