We've seen beardless Klingons before -- if nothing else, a lot of the Klingon extras in "Errand of Mercy" were clean-shaven.
Anyway, cultures change over time. We've never seen Klingons from the 2250s depicted onscreen before in either timeline, and this is a timeline that's now had 26 years to diverge from the Prime history. If anything, the ridiculous thing is when the previous shows depicted Klingon wardrobe and hairstyles being exactly the same in different centuries and different timelines. This is actually more plausible.