Hi McDerp,
If anything I would say it was the other way around.
The memory foam market years ago (and to some degree today) was dominated by Tempurpedic’s 5 lb memory foam which was more temperature sensitive and slower responding.
The newer versions of memory foam (including many of the gel memory foams) are more breathable, less temperature sensitive and faster responding because there were so many people who had temperature issues on memory foam and who didn’t like the “sleeping in sand” feel of higher density slower responding memory foams (although it’s the preference of some people such as yourself).
You can read more about some of the differences between different chemical formulations of memory foam in post #9 here and post #8 here but there are so many varieties that you would really need to talk with a retailer or manufacturer to find out the specific characteristics of the memory foam they are selling.
Phoenix