Hi ok11,
First of all I have to congratulate you on doing some great research and probably saving yourself some buyers remorse much too quickly relative to the price.
Assuming that the layers are in the correct order (which they likely are) this mattress has a poor design IMO because you would have the expense of thicker layers of latex in the deeper layers but the lower durability of 4" of polyfoam in the upper layers which would be the weak link of the mattress. While the 1.8 lb polyfoam is a “relatively” good quality material (although certainly not as durable as latex) … with the additional 2" of very low quality polyfoam on top of it there is definitely a weak link in this mattress that could be subject to foam softening and breakdown relatively quickly.
It’s great to see you found out the full specs that added up to the height of the mattress because they are different from the specs mentioned in this post and also a little different from the specs mentioned here as well (although licensee brands such as Restonic often make their mattresses differently in different areas of the country).
Even worse would be if someone purchased this mattress based on the specs here (which are almost certainly wrong) and believed they were buying an “all latex” mattress and sleeping on latex and then when it developed issues would likely believe that it was the “latex” rather than the polyfoam that isn’t even mentioned in the description.
While I understand that the “bad news” can be disappointing … you are certainly doing the right thing and some disappointment now would be much less “costly” than the disappointment you would likely have much too quickly after you purchased it.
Way to go for “catching” the weak link 
Phoenix