At the shop, we use both pressure testers and wet testers to evaluate a watch’s water resistance. It always surprises me how easy it is for a watch to pass the 30m/3 bar tests, even when it looks like the watch should fail. Watches with mangled gaskets, damaged crowns, etc., a watch can have visible signs of moisture damage inside, and yet it still passes the tests. Frustrating, when you consider that most people think 30m can handle swimming, when it almost definitely cannot. I would never wear these watches while swimming, let alone try it in the shower. For me, it has to pass a 50m/5 bar test just for me to feel okay to wet-clean the timepiece for a customer. Even then, I do it very quickly and try to minimize contact with water.
Case construction is also important. 100m/10bar with screwdown crown and casebacks, sure, should be okay for showers and swimming. 100m/10bar with no screwdown crown - I’ve seen many of these types of watches for repair because they didn’t hold up against water. Sad, but true. Based on this experience, I’m not surprised that JLC says that the watch shouldn’t be used for real diving.
It’s also a bummer that the author encountered an issue with the crown function - but to be fair JLC says it was a teething problem (which to me seems like the setting mechanism), while the author is guessing it was salt water...can’t really blame water-resistance on a prototype without more proof.