To continue, even if you have logged over 500 hours in one situation, being thrown into a completely different one can knock that advance diving knowledge/skills back into the dark ages. For example, take the diver who has 500+ hours diving in cold dark lakes and ship wrecks plus some carib diving, then suddenly throw him/her up under the ice where he/she has never been before. Can he/she handle the situation? Possibly, but because it is far different than any other situation he/she has ever been in before, there's a strong possibility of not utilizing all that experience from prior dives and losing the normal comfort level. In essence, an Advanced certification is a misnomer in that it doesn't really denote the experience level but rather where one is at in their training and potential comfort level in certain situations.
Mile Hi summed it up nicely...Bravo!