I just completed a shot-glass test using both leaf shutter and non-leaf shutter lenses to test for camera vibrations during exposure. I was surprised to find out soon after the LS lenses started shipping that the focal shutter does not open when the mirror is locked up, but have not tested to see what the difference was until now.
Boyd Norton taught me this shot-glass trick more than 30 years ago to test camera vibration (back then it was to show the advantage of using mirror lock up). We drank a lot of Bombay gin back in those days, and so I keep the tradition alive and that is what I use. Latest DF body & firmware, solid connection to a cube head, on a big gitzo tripod, ten-second delay after mirror lock-up - the gin was completely settled and calm (and I was sober, at least at the beginning of the testing). I used the three original Phase LS lenses, plus several Mamiya and Phase non-LS lenses. The shot glass of gin was placed on the hot shoe, and I focussed my eyes on the reflection of a small ceiling lamp, but it was really easy to see the surface of the gin jump when the shutter opened (likewise when it settled down).
I could see no difference in the amount or duration of the camera vibration during the exposures between any of the lenses - it was about 7/10ths of second long. There was no advantage to the LS lenses as far as camera vibration due to the big shutter slap goes. It would appear that if the focal plane shutter does open before the leaf shutter as folks have noted here, it would only be a micro second and does not make any difference.
It seems to me that we won't see an advantage to the LS lenses for less camera vibrations until the new Phase body comes out - and only then if they fix this defect in the system and allow the focal shutter to open when the mirror does - I bet the leaf shutter vibration by itself would be nil. I'm not knocking image quality of these lenses, only the fact that they don't help the vibration situation any as one might think with a leaf shutter lens.
The solution to this issue for me is to simply use long exposures (8-10 seconds or longer). That way the percentage of time the camera is vibrating during the exposure is minimal. If you do a one-second exposure the vibration would last 70% of the time. (Of course if you use fast speeds and/or flash all of this is mute anyway.)