I imagine that is there to make bottle cages sit flush with the frame. If you dinged it that much, there would be chipped paint or other, less symmetrical damage. I can't get over how much I love that color though, I bet pictures don't do it justice.
As others in this thread posted, I'm also looking at a "mid January" arrival date, and I can't wait.
I am 5'10" or so and have always been between sizes, but my most recent bikes have been Medium frames simply due to the shorter seattubes. I have relatively short legs for my height, so while the reach of a L would fit me decently for an XC bike, I couldn't think about running a dropper longer than 125mm.
That being said, a L would probably fit you better. My dad is around your height and is comfortably riding a L Slayer, after having ridden an XL Altitude years prior. If you want a long, stretched out feel for climbing, then it should work, especially if you have long legs. Just put a short stem on it to compensate and it will handle fine, and make sure you have adequate bend in your elbows, which may require a narrower handlebar.