Currently, public sub counts are abbreviated in most but not all places across YouTube. In August, we’ll make this more consistent by always showing abbreviated sub counts publicly. Creators: You’ll still see your full sub count in Studio! Learn more → http://yt.be/help/abbrev-count …pic.twitter.com/pmaKk4EU4k
As a UI/UX designer I just gotta say...what the fuck, youtube? Don't try to play this off as a design decision, this CLEARLY has another purpose, especially since it is affecting the API. No user-centric designer is this clueless.