no its not. I secretly had a mini folder with magazine clippings for my wedding when I was still dating DH, we weren't even engaged. My boss wasnt surprised when we actually did get married and planned everything in 4 weeks because I kind of had been planning it for years!
Nope, one of my dearest friends bought her wedding dress before she was engaged. Good thing she did it, since she got married 4 weeks after her engagement a few months later...