There was this one guy who lost a valuable Twitter handle due to him using his custom domain email (via GoDaddy) as a login email.[0] I'd like to think imagine Google is better than GoDaddy when it comes to security and fighting social-engineering attacks but who knows. But if Google is a weak link wouldn't that also mean all our gmails are not as safe as we think?
I'd say Google would be one of the most resistant organizations to social engineering by virtue of the fact that you can never really talk to an actual human even if you are a legit user and want help on an issue.
I don't really understand the worry here though. Aren't you always trusting your registrar when you buy a domain name? Google at least has a pretty solid track recordin wrt security.
You aren't dependent on your vendors if you can switch them out without destroying your company. The real mystery is why people turn their own businesses in to little barnacles on the skin of behemoths and expect to not get brushed off.
[0] https://medium.com/@N/how-i-lost-my-50-000-twitter-username-...