Hi monopocalypse,
Thanks for the updates and some of your findings. 
It’s nice that the Napp mattress owner responded to your inquiry with information. Transparency certainly is an important part of your value equation. All of the foams listed are higher in quality and there are no weak links in the mattress. The Hygroflex appears to be one of the newer generations of HR polyfoams that take on some of the resilience characteristics of memory foam, but have better airflow and larger windows in the foam. The GECA approval is “similar” to CertiPUR-US standards, but there are other elements for which the product is not allowed to have and there are also “social considerations”.
With the Sleep & Co S3 mattress, the Dunlop would certainly be a durable material, but of course you’d want to know more about it, and more specifically you’d want to know the information about the memory foam and polyfoam core layers that we previously discussed. Hopefully they’ll get back to you with that information.
Thanks for the updates.
Phoenix