It's also used for testing component compatibility, designing springs, cam lobes, etc.

They usually(never?) don't even have any kind of rotating assy in the bottom end, much less an induction system.

When I visited Comp Cams a number of years ago(they have 2 Spintrons), there were several "motors" from a variety of engine builders there for some spintron testing/developement.
These were all very well established big name builders.

A few of those were combos where the builders had been fighting some sort of valve train issue on the dyno or in the car and had been unsuccessful thus far, so some Spintron testing was going to be used to try and pinpoint just what the problem was.

I guess my point is......even some of the bigger names in the industry use the Spintron to figure out what's really going on with the valvetrain........and the Spintron has no provision for creating the combustion pressures and shock wave tuning inside the manifold.......so it's unlikely those things have a big impact on the results.

Another way to look at it is........if you're having a valvetrain stability issue.......I highly doubt it's the combustion pressures or the tuning pulses inside the manifold that are the cause of the problems.