There are a few keyword mismatches in the game, usually from earlier sets before a keyword became "a thing." For instance, Long Drong's Pirates, who get buffs off of "Slayers" are newer than the Slayers of Karak Kadrin, so when Assault on Ulthuan was designed they might not have been thinking about the Slayer keyword very hard. We are starting to see the keyword "Elite" more frequently than makes sense, so maybe we'll see an "elite" buff card later. But if that happens, then there will be all sorts of arguments about which cards should be errataed as "Elite" if cards like "The Greatswords" are elite.
On whether to errata keywords: I think that would be super annoying to new players (not like I'm awash in new players at my play group or anything but…), basically remembering card ability changes is one thing whereas remembering "Oh wait, that guy is a 'Warrior', and that guy is a 'Knight'" is harder. It would also be super annoying to me to be in a situation where a zone burning relies on keeping straight that some card classifies as another type (not shown on card) which in turn activates the ability on another card. Sooooo, basically, I am of the opinion that as long as they keep printing cards with traits that make sense I'm happy, but the retroactive re-classification is probably more "busy work" than "game enhancing work". Bias: I hate having to remember MRPs.