Two Meetings Simultaneously

An invitation was sent to a team meeting.

Some team members reported that they were in a meeting during the scheduled time, but not the meeting.

My theory is that they joined a chat once the Teams app was running rather than selecting the meeting link from the invite.  And my assumption is that the link in the invite is unique, and therefore all selecting it would end up in the same meeting.

Any help bringing clarity to what occurred much appreciated.

Many thanks