So
The phone screens that broke without peeling the protective layer are most likely user mishandling.
The one with the bulge under the screen is likely caused by hardened clay that got into the hinge. The reviewer used moulding clay to secure the phone for taking videos and pictures for the review and the clay likely got into the hinge via the tiny opening and the folding action pushed the clay up to the screen and eventually broke the screen. If you see the video by Lew, 3 posts from this, clay is a very common item used by reviewers to prop up the phone for taking views of the phone for video and pictures of the review. For regular consumers, it could be larger dust particles or lint or even sand particles that could get into the hinge and potentially result in the same outcome.
Samsung will have to work even more on the design of the Fold for future iterations if any.