That sounds like BS to me. The only thing I can see happening (and it almost happened to me once) is if the circlip that is used to support the lower spring perch on the Koni shock is not properly installed, it can shift and possibly allow the spring to push the perch down.

I caught one of mine during a pre-track inspection a few months ago. I hadn't fully seated the circlip in it's retaining groove and it was half way out of the groove in the shock. The spring perch (GC threaded barrel in this case) had cocked down on that side. Everything was still together, but the top of the threaded barrel was rubbing against the inside of the spring. A few good hard bumps could have dislodged that circlip, or possibly vibration could have caused it to break... that corner of my car would have taken a nose-dive at that point.

But, other than that issue, I don't see how the springs themselves are going to "pop out" of the upper or lower spring perches unless you get the car completely airborne. Generally speaking, if you do that with a street car, you'll have other things to worry about besides your springs being seated.