Well, taken as a dogma, this is not true. A sequence diagram (SD) shows the behavior of objects in a messaging method (as well as their life time and some additional additional information, if necessary). You can also use the sequence diagram to describe scenarios in use cases. But, simply put, SD is more technically oriented (design / programmer class) rather than business (business design / stakeholders). To visualize a use case, you are better off using activity diagrams (AD). And even better if you immerse yourself in BPMN (which takes AD to a new level).
It is possible, however, to convert AD to SD and vice versa without loss of information (if you forget about the above bits and pieces).
: . , ( ) (. Cockburn Bittner/Spence), . , UC, . , AD . UC (, ), (, , , , → , : ?).