Yes, that sounds like hyperbole.

People do want to bookmark tweets. But Twitter reasoned (probably correctly) that people "like" a lot more tweets than they bookmark. Naturally, Twitter likes the idea of visible engagement, so they are encouraging people to do the lighterweight thing.

What's interesting is that I had already found my own behavior changing. For years I used 'favoriting' as bookmarking...but in the last year or so, I've changed and was already using it as a show of appreciation. I wonder if many other people were doing the same thing already.