Hi Friedrich,
I’m guessing you’re referring to the new transition layer of 1.5" 2.5 lb. polyfoam on top of the 5" 1.8 lb. polyfoam support core (the core used to be 7" and there was no transition foam layer). While I don’t have the specifics on the IFD of this layer and I haven’t tried the products side by side, it certainly could be reasonable to assume that this transition layer could “soften” the transition from the upper comfort layers to the base support foam layer (and the fact that the base support foam layer is 2" thinner.).
With that being said, I would be very cautious about using someone else’s experience on any mattress (either positive or negative) as a meaningful source of guidance about how a mattress will feel for you because firmness and softness is very subjective and relative to different people (a mattress that feels firm for one person can feel soft for someone else) and each person can be very different. There are also different types of firmness and softness that different people may be more or less sensitive to (see post #15 here) and a mattress that is a “perfect” match for one person in terms of PPP (Posture and alignment, Pressure relief, or Personal preferences) may be completely unsuitable for someone else to sleep on … even if they are in similar weight ranges. Using other people’s mattress reviews or experiences as a meaningful source of research and information can often be more misleading than helpful (see post #13 here).
If you want to look, a forum search on Casper (you can just click the link) will bring up all the forum posts and feedback that mention them.
Thanks!
Phoenix