Because there is no industry accepted definition of "Survivor Stock" it means what you think it means. I think it's used as a catchall phrase to insinuate that the bees do not require human intervention (ie, treatments). To me it's a form of marketing where a catchy phrase has been issued that can be interpreted in multiple manners but actually promises nothing. As three examples, look at Miller Lite with "triple brewed", Nike "Just do it", Obama, "Yes we can". What does any of that really mean? Nothing has been promised about the respective product and quality or performance has not been proven nor even discussed.
Unfortunately it's buyer beware as there's no way to prove they've never had treatments of any form, and past performance is not necessarily indicative of future performance. Remember, the queen is mated with unknown drones therefore 1/2 of what you're buying is not really tested. I'm not saying the queens aren't good, but don't buy in to believing the "survivor stock" moniker.