Hi Pea,
I don’t think it’s the standard that is different as much as the design. There are many factors that contribute to the feel and performance of a mattress besides just the ILD of the latex layers and ILD (or density in the case of Dunlop in many instances) is only one of them. This is also why the options you have available after an online purchase can be an important part of the “value” of the mattress.
It’s a good thing that the mattress you purchased is too firm rather than too soft because you have many more options available to fine tune it. Post #2 here has some suggestions that may be helpful.
The dimensions of the latex are probably correct but latex is very easy to stretch when you pull it and it “sticks” on the layers below it so I would “wave” it into position so that the layer isn’t stretched beyond it’s normal measurements. The cover is designed to be tight and this helps the mattress keep it’s shape. It will loosen to some degree as you go through the initial break in period.
It may be worth exchanging the top layer (depending on the density or ILD that you have) but this would depend on identifying exactly what you are trying to correct, how much it needs correcting, and on the specifics of your mattress and the options you have available. I would also make sure you had slept on the mattress for at least several weeks (which it seems you have) before making any changes and eliminated any of the other options that could be contributing to what you are feeling. the most effective way to decide on any changes that may be necessary and the options you have available is with a more detailed conversation with the manufacturer.
The odor is the smell of natural rubber and this is normal for Dunlop yes. It’s not a “chemical” odor but just part of what natural rubber smells like. It can be longer lasting than the sweeter smell of Talalay but it will dissipate over time.
If some of the other suggestions aren’t effective and depending on exactly what you are looking to change and the degree of change that is needed … then either exchanging a layer or adding a soft topper can both be effective in softening up a mattress that is too firm.
Phoenix