Where the springs measured correctly? I'm not doubting you, I'm just curious. Because the way the OE springs are shaped and mounted, you have to account for the dead ends at each end of the spring. The way I would test would to have the springs mounted on a stock damper. And then do the test you spoke of.
I have never measured the stock spring, I never felt the need to. And the numbers never looked weird. With the rates that I posted above, natural frequencies look right, wheel rates look about right, balance looks right. None of the numbers looked out of place.
I was hoping I could find that rates listed in the TSRM, but I couldn't seem to find them in there. I thought I found them in something else that looked more official than some dudes website, but I have had them written down for a while now and don't remember the original source.
But either way, the stock rates don't really matter. If you know what you're looking for out of the car, everything can be done from scratch. The only time I ever use the stock rates for anything is to look at how bad the balance is with those springs. Other than that, if you know you weights and geometry info, you shouldn't need stock spring rates for anything.
And the response time, was that on the same shocks in the same condition? That will greatly affect response time.
Tim