Yep, that's correct, Jonathan, unless the lead qualifies for a segment that is higher prioirty (in that case, it will still be in that segment).
E.g. if you your segmentation is (using the below for demonstration purposes):
1. industry = Finance
2. Company Size = <100
3. Country = China
If a lead's country value changes from U.S. to China and the lead does NOT satisfy 1 or 2, then it will automatically fall into segment 3 when the value changes -- just like smart list behavior.