That's a phrasing I'm coming more and more to dislike.
My driving skills are entirely inadequate for driving on a race track, or baja, or for doing hill climbs, but they are not lacking at all for driving on my prosaic daily commute.
Adequacy is determined by application. Of course an non-cave diver's skills are inadequate for cave diving. If they weren't what would be the point of teh course?
I'm not saying people are not qualified for the environment they came from. I'm saying that when they're shown a new bar, many begin to realize they're not the diving god they thought they were up until that point.
Just because I don't drive a race car doesn't mean I'm not a decent everyday driver. And just because I drive every day doesn't mean I'm a good driver either. If you want proof of that, think of how many people you curse under your breath on the way to work every morning.