Blackcrusader
Contributor
The confusion here is the difference between "allows" and "recommends." PADI says an OW card certifies you to 40m, but they recommend not going to 40m -- or 30m -- without additional training and experience. PADI does NOT control -- and cannot control -- what you do except while you are being trained.
AOW trains you to 30m; Deep trains you to 40m. Deco trains you to exceed your NDL.
What a dive operation or resort or a boat might request of you in training -- "certification" -- to allow you to go to some depth, or dive at night, or use certain equipment, is up to that operation or resort or boat (it is not up to the training agencies). But they are being arbitrary when they do that and have no basis for making such a demand. Other operations/resorts/boats will have different rules.
Some of the confusion between "allowed" and "recommended" is driven by fears of liability and enforced by insurance companies.
Yes, sorry, it is indeed confusing to new divers; it is confusing to old divers, too.
Training is always good. I did hundreds of hours of training over many courses as have many divers over the years. Outside of training though it is doing hundreds or thousands of dives that gives us experiences that dive training does not always give.
Have you seen training dives for a certification take people on fast drift dives in up and down currents?