Hi AT,
Your salesman is probably genuinely trying to provide you with the information that he believes is correct but I suspect that the source of his information may be incorrect. “Natural” Talalay generally refers to blended Talalay which would be a blend of about 30% natural rubber and 70% synthetic rubber (although there would also be other substances used to manufacture the latex such as curing agents, foaming agents, and possibly fillers as well … see the first part of post #2 here). There is more about the different types and blends of latex in post #6 here.
There are certainly some people that can sleep warmer if they are sleeping directly on thicker layers of softer foam materials (even latex in some cases) without a more temperature regulating quilted cover on top of it (such as wool). There are some comments in post #6 here about the pros and cons of thinner more stretchy covers vs wool quilted covers.
I really would make sure you know the specifics of every layer in your mattress and I would keep in mind that latex cores are only poured in 6" thicknesses or less so there would be several foam layers in your mattress (either latex or polyfoam).
The law tag would be on one end of the mattress and your salesperson can show you where it is (it’s not legal to sell a mattress without it). Many stores put the end of a mattress that has the law tag against a wall so that their customers can’t read it.
Phoenix