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
Seems like a direct response to the rise of subscribe comparison live streams. YouTube probably did this change in hopes to remove the "toxicity" surrounding the YouTube sub count system. Overall a bad idea for creators designed to depersonalize YouTube.