I'm sure it's just because it's so new nobody would be looking for a replacement battery this soon on a brand new vehicle hence they haven't updated their catalogue but they will soon I'm sure. I really wouldn't worry about it this soon, why would you want to replace a perfectly good practically new battery? Are you having issues with it?
I'd say the oem battery should be just great for many years but I dunno I guess it's possible they put a cheap one in to start. I only say that because I'm surprised how crappy the oem tires are, just god awful cheapo continentals I would have expected better on my limited trim package they could sprung for something decent but oh well, tires can be replaced same with the battery, but I am not replacing mine this soon. Going to put at least a little wear on these tires and battery first, I am not made of money lol