Hi Manimal,
He’s correct that Dunlop has a different feel and response curve than Talalay. There is more about how they compare in post #7 here and using Talalay in the core could make “enough” of a difference that it didn’t need a transition layer compared to a similar firmness level of Dunlop (which would “feel” firmer and less resilient).
A difference of 4 ILD is also very small and for many people if the 40 ILD core was too firm then switching it to a 32 ILD medium core (two firmness increments rather than just one) could make enough of a difference that they didn’t need a transition layer.
You’re right that I normally focus more on the materials in your mattress than on which manufacturer you may be dealing with so I don’t normally try and figure it out or think about it. I just assume that you will mention it when you are comfortable doing so. Whoever they are they are certainly taking the time to work closely with you!
Phoenix