Hi Mrsbitterchef,
I would want to know what was in the missing 2" partly to make more meaningful comparisons with other mattresses and partly because it’s possible that 2" of a lower quality and less durable material could be a weak link in the mattress. I would always make sure that the specs and layer thicknesses add up to the thickness of the mattress (within about 1/2" or so to account for normal variations in thickness and cover materials).
The choice between different types and blends of latex is generally a preference and budget choice but 100% natural Talalay is certainly a high quality material. There is more about the different types and blends of latex in post #6 here.
Phoenix