Suppose an external consultant is working for a company. Why would a manager for that company ask about his citizen status in a 1v1? Is that a sign that that the company wants to hire him?
It could be a sign of interest in hiring you.
But depending upon the nature of your work and the industry it could also be asked to determine if you are eligible to work on sensitive projects or information. Or if special security considerations are required due to your citizenship.
In all honesty, as @Job_September_2020 says "Only he would tell you for sure"