Why didn’t they discuss the possibility that it’s locking up and getting more tension building up???
That's what he was talking about - "elastic deformation". This occurs when the fault is "locked up" due to friction and the surrounding rock gradually deforms as more and more stress is placed on the fault until it finally slips. From what he's saying, there could be a certain amount of stress on the fault, but it is not increasing, as indicated by the lack of increased elastic deformation in the surrounding rock.