Yes, I do this all the time : first unfold the camera and then spool the film to the next frame and then do the settings and shoot. But not only for the reason you give, also because the "wind" generated by unfolding could sometimes lift some "dirt" inside the camera and settle it on the film (yielding "black" spots - opposite of white spots due to dirt on the neg under the enlarger - or the scanner).I read that you should not wind the film to the next frame until just before you plan to take a picture. If you close or open the bellows too fast, you create a vacuum that pulls the film out of the focal plane. Advancing the film AFTER you open the bellows puts tension on the film which ensures it lies flat in the gate.
As for "focusing errors", are you sure that these actually are ? i.e. that what you want in focus isn't but some other plane is ? Because my experience of such MF folders (a Moskva V - russian copy of the Super Ikonta) is that most often, lack of sharpness is due to "microscopic" movements caused either by "my nervousness" or by tiny vibrations of the lensboard on shutter release (paradoxically, these vibrations may have a strong effect at the fastest shutter speed of 1/250, because the shutter springs of these old compur designs are then pulled very taut). To damp these vibrations, I use to hold both the lensboard (with one hand) and the body of the camera (with the other).