For what it's worth I think there is a lot to be gained by understanding how wheel frequencies actually work in practice, however a 2wd buggy front end kick up creates so much mechanical resistance against the purely vertical motion that the bench test described is going to give some misleading readings.

Buggy springs may seem "stiff" at the front in that test, but I think we would mostly agree that kit settings are not far off in practice.

I seem to remember reading that when Gene Husting et al were designing the RC10 40 years ago they built themselves a "suspension Dyno" that was a few strips of wood on a board. They got the rates pretty good for the day of release, this shocks and springs were still under world champion cars 20 years later.