I haven't tried it, as you get asked for the answers to common security questions, and supply a voice sample. You could lie but many people won't. My other issue is that it will have been trained on a large number of voice samples and no one will learn how to distinguish different accents by using it, or even by developing it. An alternative, knowledge-based approach, would work by splitting the speech into phonemes…
Have we tested the same website? You don’t get asked anything. You just read a text.
So I tried it. It guessed (correctly) that I'm a native English speaker. It only tells you which foreign accent you have.