The attack pattern is: 1) User goes to BAD website and signs up. 2) BAD website says “We’ve sent you an email, please enter the 6-digit code! The email will come from GOOD, as they are our sign-in partner.” 3) BAD’s bots start a “Sign in with email one-time code” flow on the GOOD website using the user’s email. 4) GOOD sends a one-time login code email to the user’s email address. 5) The user is very likely to trust…
Somehow this makes me think of Pascal's Wager...
You just got through describing an attack where the victim was not aware that a bad actor can trigger a bona fide password reset code at an arbitrary time. For your little table of threats, you posit that at least clicking the link goes to the bona fide web site.
But there's a separate little table of threats for the case where an attacker controls the timing of sending a fake email. I believe realtors have this problem-- an attacker hacks their email and hangs back until the closing date approaches, then sends the fake email when the realtor tells the client to expect one with the wire transfer number/etc.