Yes, that was my understanding. In order to test positive for the antibodies, you had to actually have the virus at some point. Maybe Doc can clarify.
If that's true, it means many, many more people have had the virus than the denominator currently being used. And that means many people with the virus have few or no symptoms. All that makes sense to me because up until now, the only people being tested were sick people with symptoms. So the reported mortality rate was really, "Of all the people sick with serious symptoms, X% die". Now we're learning, "Of all the people with the virus, Y% die". There's a difference, and it seems like a significant difference to me.