When comparing fancy colored stones, remember there is a large range of color within each grade, as well as a difference between grades. So, for example, your Y-Z may have just missed being a fancy, and their small fancies may have been on the lighter end of their grade, lessening the gap between perceived color differences. Also, size (as well as cut, as we all know) does play a role in the appearance of color. And, as a thing of nature, each stone may appear darker or lighter than its [unset] grade may indicate... light and color are unpredictable.
I think the blue box store is like any other big retail store... they have great sales people and terrible sales people, regardless of their training. And, as the blue box store has a ton of sales associates, I am sure they have their share of crummy people, and people who just can't get over themselves. Too bad. Honestly, I have encountered some marvelous blue boxers over the years. Of course, they can't bring what David has to the table, but then, we are not comparing comparables, are we?
As far as GIA training, I can tell you first-hand that the way the blue box sales person approached you is NOT how GIA teaches salesmanship (and I am sure it is not in the blue box manual either)! It could be that the comment about how heavy your earrings are was meant as a casual opening to initiate conversation with you... however, it certainly was a stupid remark to make! As far as technical talk, there are things and certain phrases that a trained sales associate must tell you (to meet FTC guidelines), un-factual things they can not say, and then, there are methods they are trained to use in order to sell the "romance" of gems and jewelry. Most people do not have your knowledge, so I am sure that the thoughtless, pat answers of a poor sales associate may suffice for many shoppers – especially if they are thought to be "just window shoppers" (another mistake many sales people make – dismissing potential buyers). Most likely, your associate felt intimidated by your knowledge and didn't have the experience or ability to deal with her personal insecurities.