I think anything can be taught by the right teacher, then ingrained by the right dedicated practice.
All depends on the time the student has, or the standard of coaching. I'm not going to give my opinion on how to as it's Brian's site and I respect site rules but if you train to be strong and fast enough then flat and laid off coming into the ball is a powerful position to be in. If your arms and wrists aren't strong, and your pivot isn't up to much then it's difficult to recommend it, and not one for the once a week chopper......
Every good golfer drops it laid off, open and deep coming down. There will always be exceptions but the majority of decent ballstrikers in this world all do it and always have. Whether it is done going back or coming down is personal preference. Those that do it more hit it straighter (Joe Durant), but not as far.
To see where most golfers are requires you to know where they were aiming when you look down the line, but that's a conversation that could go go as to where the camera should be.
For anyone to say Sergio did a "silly thing" at the top I feel don't know what he was doing, and trying to make Sergio swing "conventional" a recipe for him never ever ever reach his potential.....
What you "do naturally" was learned is the first place....and any new move is simply learned in the same way. The book "The Talent Code" does a great job of explaining this.
"Natural" golfers just happened to work it out for themselves like a lottery winner picked the right numbers. Beyond actual physical handicap any move in the golf swing can be "learned" ( even a tripod, which I don't belive in
) but not many golfers will spend the time doing it properly and ingraining it.