Back rest vibration test

I tried something, well it kind of just hit me. I decided to bleed the pressure out of my shocks, left first then right. When I bleed the right the bike actually dropped a little. Enough to actually see it. This goes back to putting pressure in with rear tire off ground.

So I put 25 lbs in both and took wife for ride. She said the vibration was there and very noticeable. I then came back and emptied them to zero and we went for ride, no vibration what so ever she said.

My thought is, putting equal air in them with tire on ground causes a uneven balance with bike having more pressure on left side shock. I dont know, but it worked.