For most of my cameras, when triggering the shutter with my finner, I have always held the shutter button "in" "down" depending where it's located until the cycle is complete. Even the Rolleiflex cameras I do the same. Does it prevent jerky motion? I think it does, at least to me it does. Perhaps I'm wrong but my thinking is that one movement, pressing to trigger the shutter, helps prevent slight movement as compared to press to trigger and immediately release where if you have a fast finger then there could possibly be movement when releasing it.
Maybe I'm full of hot air but it's what I have done for many years. At least a million of them!