These torture tests are interesting but painful to watch. Consumer Reports also has an article “The science behind smartwatch scratch resistance” about how they did the scratch test and what it means.
Bottom line? “The face of the Apple Watch is definitely harder than that of the Apple Watch Sport. But the performance of the hardened glass of the Sport model is pretty impressive as well.” It sounds like, as long as you take the usual amount of care with your expensive electronics, the Apple Watch screens are pretty durable.