I've never had a PCP that would bulge the pellet skirts like the springer did. From that I conclude that the springer reaches higher pressures at some time in the cycle.
It's also the case that springers can get a pellet up to 12 fpe energy with far less air than a PCP uses, and often in a shorter barrel. If the work done is the same, i.e., 12fpe output, and it's done in a shorter time, then the peak effort going in must be greater.
Sorry to disagree with the Cardews, though. If you do the sums on the springer compression you find that a pellet that resists movement until the last moment will see a pressure far higher than 94 bar. Sure, if it's a loose fit and starts on its way long before the end of the piston stroke, the pressure doesn't reach those levels. Maybe that is what happened in Cardew's case. Their approach was experimental rather than analytical in some respects.