I've taken a look at the video and honestly; the Elf looks fine and very natural. Granted the arms look a little awkward when in motion, especially considering how fast he's moving his arms, but when he's standing still his physique is pretty much identical to mine and the majority of North-Western Europeans for that matter.
I've seen people call the Elf "Anorexic, looking like a 15 year old and as having muscular atrophy," which is a little insulting, considering the fact that I and many others look just like said Elf, and I can tell you that I 'ain't skippin' no meals. But let's put that aside, because I'm sure that wasn't intentionally insulting! 
I'm very happy to have a character that's just plain slim, more so because I always create characters resembling myself, so!

I'm kind of curious if the people who find male Elves excessively skinny are predominantly from North America. Not because LOLMURRICANSRFAT but because your average American has a somewhat chunkier, bigger build than North-West European. Oh well. Like others have said before me, there's always Humans!