Not a clue. I didn't make a statement regarding anything for sale, I compared coilovers to a coil-shock set-up. And I stand by it, with the same spring rates and shock tuning, they would ride identically (didn't say nor do I mean that you could go out and buy that identical set-ups however), actually, a coil-shock set-up might outperform slightly by virtue of the larger diameter coilspring and the ability to run a bypass shock but that's most likely beyond the scope of the question posed.
A coilover, by virtue of being a coilover, will not outperform a coil-shock set-up. Where a coilover excels is its tune-ability and packaging. The ability to dial in the perfect spring rate (be it a single, dual, or even triple rate depending on application) for the vehicle at the perfect ride height combined with vehicle specific shock valving. That can be done with a coil-shock set-up but dear god it'd be prohibitively expensive.
And to your point directly, which I didn't comment on in the post you quoted, I don't have a clue what spring rates anyone sells because I'm not aware of a single lift kit manufacturer that actually publishes their spring rates. Pretty easy to tell what spring rates are on a coilover because it's written right on the spring, but most coilspring-shock set-ups have long been stripped of that data.