I think the binoviewer will result in a higher magnification and need a tighter collimation. The weight of the binoviewer may also flex the focuser slightly, so collimation with the binoviewer in place may compensate for that slightly.
Binoviewers magnify any type of optical problem. So a good collimation is good for them.
I do not believe that switching back to a 2" eyepiece will shift the collimation enough for you to notice.