Thanks for reaching out to the Zoom Developer Forum, I am happy to help here!
Yes, it is an expected behavior. Each occurrence will generate a unique UUID, because each meeting has its own instance.
Also note that when you call GET/meetings/ you are getting the UUID generated for the next occurrence and with GET/past_meetings, you are getting the UUID for the meeting instance/occurrence that already passed.
I am linking here a useful guide to understand meeting IDs and UUIDs.