Hi Coventry,
I feel that the company should have disclosed or educated it's customers in the product description about this substantial change.
They are doing both ... and disclosing the details of the material to those who understand the importance of asking (which is an important part of any mattress purchase) and they are in fact educating people about why they believe the current material is better in many ways than the one it replaced (more resilient, better conforming, and for the record not less costly than the previous foam they were using). Like any material there are always pros and cons to its use. In strict durability terms if you were sleeping directly on the support layer then the current foam would be less durable than the previous foam but you don't sleep directly on a support layer and for most people ... the current foam is an improvement in several ways that may even increase value to a customer.
If you talk with them (as every purchaser should be doing with any mattress purchase instead of mostly paying attention to reviews in the first place which is among the worst ways to choose a mattress) then they will both disclose and educate ... to the degree that may in some cases can even cause them harm when those who are only familiar with one aspect of foam quality and performance come to believe that what they know about is the only thing that is important and criticize them (or worse yet change their review) based on limited or incomplete information about the real nature of the change. Would you really be saying the same things or changing your review if you knew that the change was an improvement for most people? I can certainly understand adding the information you did in your review (saying that the mattress has changed since you purchased it) but if the change really is to a better more suitable material in many cases ... then are you so certain you know enough about all the different factors in foam quality to make these kind of judgements and deter people from making a purchase that for them may even be better than the mattress you purchased?
I understand your point certainly and you are not the only one who may feel the way you do if only density is considered but most one dimensional evaluations are usually not that accurate or even meaningful and density is not the only criteria of quality (particularly in a base layer). It's one part of a larger picture. It's also based on some assumptions (that it's an inferior material) that are not accurate or at least incomplete because it is better in some ways and worse in others and is a matter of tradeoffs more than "better / worse" evaluations. For the majority of people it is a better choice ... for a few (that are in heavier weight ranges and "go through" the upper layers more and where the durability of a base layer may be more important) it may be a worse choice.
Sometimes information in a vacuum that only looks at one part of any issue to the exclusion of the rest can end up misleading people as much as it may help them.
"Better for most and worse for some" would be a much more accurate description of the change they made and each person is in the best position to judge for themselves whether this would make a suitable choice for their specific criteria compared to what else is available to them in the current market.
Knowledge can be empowering (and is the fundamental premise of this site) ... but it's a two edged sword and incomplete or partial knowledge can also be self limiting.
Phoenix