No special technique is required. But nevertheless, people do damage threads, as I’ve repaired many of them. The brand doesn’t matter, it happens across all of them, so they are either all “sub-optimum” designs, or people make mistakes occasionally. I know which option I’d put my money on...I've been wearing screw down crown watches daily for the last 40 years without incident, one Rolex, one Omega so IMO it doesn't seem that hard to perform that operation without stripping the threads. But, it also seems to me that unscrewing a crown and screwing it back in again is a common enough practice that the design should be such that the threads engage reliably every time without requiring any special technique to ensure they've engaged properly. In other words, unless the user is extremely careless it would seem to me that stripped threads are more indicative of a sub-optimum design, rather than user error, so I'd be upset if it wasn't covered by warranty.