So If I understood you correctly, the sequence would be:
The user belongs to Segment 1.
The user qualifies trait B.
The user quits Segment 1 and joins Segment 2.
I am sorry to insist, but the part of quitting a segment is pretty important for our project. How often is segment belonging evaluated? Every time a user qualifies a trait?
Thinking about these doubts makes me wonder the behaviour of AAM in another scenario. If a segment is defined by traits A and B and after some time, those traits are replaced by traits C and D. All the users a re-evaluated after changing the segment?