Hmmm. What does the login API return as a status code. My guess, from reading the docs, is that it returns a 212, as specified here: https://fusionauth.io/docs/v1/tech/apis/login#authenticate-a-user
This is still a kind of success, and if you are using the Login API, you are expected to consume the response codes and make appropriate limitations based on that.
Does that make sense?
If, on the other hand, you are getting a 200 for this user, that seems like a bug. Or at least something is going on that I don't understand.