I believe solution to this topic title is in the previous post - you don’t need to use two OIDC’s, rather one OIDC and one Microsoft_auth.
microsoft_auth_email_verified would not make Microsoft Auth behave like the already-configured OIDC flow itself. My understanding is that it only makes Discourse treat Microsoft-provided emails as verified/trusted by default, which can help with account linking / avoiding duplicate accounts if those emails are genuinely verified:
For the button text, OIDC is definitely under the js.login.oidc text namespace:
And Microsoft Auth appears to use the microsoft_office365 translation namespace rather than oidc - for example this bug report mentions en.login.microsoft_office365.name:
So I think the relevant text key namespace for Microsoft Auth is microsoft_office365, not oidc.