If you, are targeting a specific account, as an attacker, if you were to spoof a 2FA disable request for every likely email, this would be obvious to the human who is receiving the emails, and would raise a red flag. So, if they A. Get your login credentials, B. Obtain the email address you used to open your account, C. Spoof the email succesfully THEN they could access your account. Which means that they have to 1. Get your login credentials, 2. Defeat the 2FA.
Step 1: Get your email account compromised.
Step 2: Attacker uses password reset form: "Reset your password -- Enter your email address -- Click here to reset your password", so they now have your account credentials... you don't, just them.
Step 3: Attacker sends a nice email to support@bitfinex asking for the 2FA to be disabled, and is able to follow up with any further exchange of emails.
So in the event of an email security failure, your security model ends up resting largely on the idea that your support staff can tell apart a hacker from a real user. If they ask sufficiently probing questions before complying, maybe that isn't too bad an assumption (it's still a bit dodgy from a formal security point of view, but pragmatically might at least pass a sniff test), but it would be reassuring to know that there's some sort of actually-rigorous process employed to be certain that you're talking to the real account holder.
For verified accounts, you
have identity-establishing documents to refer to. I'd feel comfortable ticking a box that said "Please require me to provide that same sort of documentation again before disabling my Authenticator".