Aside from the dingy itself, there's an engine, and some people use it as after-stern locker. When the boat is trimmed for an anchor and 200' of chain being in the bow, maybe the combined effect is put the stern in a more vulnerable position?

I've been on a couple of boats that had a wave break into the cockpit from after of the stern quarter. Fortunately was only the 12" of water that cleared relatively quickly. Never in an anchorage.

I was surprised by your experience, Steve --- especially in an anchorage. It could have been a "freak" conflunece of short waves and "rebounds" off the shore of the anchorage. Or, maybe you need to think about the davits.