Never had an issue with mine or with anyone I know who has an Apple Watch. Oh well.
No issues with the countless people I know who own them.
Spent more than 2 weeks in the remote jungles of Honduras, in +95º heat and near 100% humidity every day, working outside in the sun. Never had an issue. If anything is going to loosen industrial glue used on the screen, it'd be that weather.
While I'm not saying this screen issue never happens, it's certainly not widespread enough to win a class action suit.