Not new, and not unique to Trek. 14 years ago, and 8 years before that, the manual that came with my new bikes we 2 pages of "Isn't this a great bike?", 5 pages of "Don't ride the bike, it could be dangerous" warnings, and 10 pages of "Take it to your dealer to get it serviced."
Maybe not the seat height adjustment. Maybe I was capable of tightening the seat clamp. But I'm not sure about that.