That's new, and did not exist when I setup my domain. But if I understand that link correctly, if you do this you'll run into the "sent via Gmail" problem the

That's new, and did not exist when I setup my domain. But if I understand that link correctly, if you do this you'll run into the "sent via Gmail" problem the parent poster alluded to, as Google Domains will not issue you a new SMTP username like with GApps. With my version, I'm actually sending mail via the GApps user (and my domain), not the Gmail one, and my Gmail account name is not revealed in the headers.