The National Geographic Society has a page describing beaches that focuses on ocean beaches but nonetheless seems to cover many scenarios. Would its description of a beach berm be included in the natural=beach tag in an ocean environment?
This description doesn’t seem to cover beaches around lakes or along rivers, and of course it doesn’t cover artificial beaches. But I like how it gives a diverse set of examples.
I know you tried to clean up the wiki, but the assertion that the tag natural=beach should only be used above the coastline is still on the natural=shoal page and maybe also elsewhere, so the Wiki currently contradicts itself on the topic. If we want to make the Wiki consistent, we might have to systematically look for other occurrences.