Standards change and improved methods are discovered. In the 50s and 60s the "hip belay" was the standard and considered safe. Once ATC/tube style belay devices became ubiquitous, the "pinch and slide" technique took over. The "pinch and slide" technique you likely learned is no longer considered the safest method of belaying. The AMGA belaying technique is now considered standard and for awhile gyms would still pass "pinch and slide" users but I'm not surprised they have stopped.
Safety standards do change for the better, but insurance and legal risks do have gyms on edge. I think his point is that gyms tend to be overly strict in areas that do not matter, but are easy to regulate/check. I.e requiring you have an unnecessary “backup” knot above your figure 8, requiring 2 Tri-locking carabiners for autobelay in response to accidents where people simply didn’t clip into the autobelay, knowing your gyms mnemonic for checking your knot, and disallowing wearing a single earbud when autobelaying (saying you won’t be able to hear if there is an emergency). These are all things I’ve seen required in gyms that IMO do not actually improve safety. Having friends that work in gyms, I’ve heard a lot of these policies are due to demands by insurance companies.
Meanwhile, I very frequently see people belaying in manners where their climber would hit the ground if they fell (usually the first 3-4 bolts up). The difference is, this is much harder for gym staff to notice and correct. Furthermore, I’m sure most of these climbers are capable of using better technique and do so when taking a belay test, but then get complacent afterwards.
