I got the same feeling. When I picked up my 3 wood the other day with the Marix Ozik HD 7 stiff shaft, it also felt whippy. Tried it in the sim and was smoking it 260 in the fairway so it worked but it did feel whippy when waggled though.
I think my driver and my 3 wood influence the thoughts on the shaft. Both my Driver and 3W are stiff stock shafts but when I waggle and just kind of whip the club back and forth you can really see the flex and feel it, when I do it with the 4w there is not as much whip in the shaft as my other two clubs. My Driver and 3w actually felt really whippy compared to this so I feel the blur is actually stiffer in my opinion.