The URL below states that the The remember Multi-Factor Authentication feature is not compatible with B2B users and will not be visible for B2B users when signing into the invited tenants.
In that case, is it correct to understand that the cookie issued when "Yes" is selected in "Keep signed in" is valid regardless of the above functions?
https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-mfasettings