Choo Choo! Here comes the BULLSHIT TRAIN. All aboard!
For what it's worth I'm pretty sure the change was you, not Google. Google's business model hasn't changed. They are still an ad reseller, just like they always have been. They still don't sell your data, just like they never have.
Automatic account merging still doesn't happen, just like it never did. Google didn't link your friends accounts together, your friend did. And if you for some reason really, really want a different account for youtube and gmail, Google is perfectly happy with you doing exactly that. And there's somewhat reasonable multi-user support to help you do exactly that. And chrome's multi-profile support allows for even stronger walls between accounts. In the particular case of youtube they even let you use a different identity for youtube from the rest of Google, your "gangstakilla999" friend just didn't choose that option when asked when he was merging accounts.