Opening the bellows before you turn the knob is such a trivial thing to do. Even if there is little difference or even no difference at all, the solution is so simple and virtually without cost that there is no reason not to do it.

I will try to remember to operate the camera in that order but, if I forget... what the hell?
As time goes on and I get more and more pictures out of the camera, I'll see whether it makes a difference.

It's good to have knowledge and understand the possible ramifications of doing things a certain way versus another but you have to keep things in perspective. Right?