Hi mistifa,
It would either be cost savings (so they only have to keep one thickness on hand) or because two convoluted layers will feel and perform differently than a single layer (a single layer would only be convoluted on the top of the layer not in the middle and this would affect the feel and performance of the mattress).
Both of the mattresses you are considering use good quality materials and there are no obvious weak links in either one so a choice between them would be based on which one was the best “match” for you based on your testing for PPP and the parts of your personal value equation that were most important to you. The Telluride has 2" of latex under the top polyfoam quilting layers so it would probably have an edge in terms of durability compared to the Doctor’s Choice.
Phoenix