You are correct.
A joint account is owned by both persons; when one dies, the other becomes the sole owner, and a personal representative cannot touch it as it is not part of the estate.
The same goes with any accounts by a single person that might have had a POD notation, the funds go directly to the beneficiary, and are generally not part of the estate.
I hear and I forget. I see and I remember. I do and I understand.--Confucius