Hi Wavycat,
Convoluted foam will always be softer than the same ILD of foam that isn’t convoluted because much of the material has been removed and the portion of the foam layer that is convoluted will be softer (less material to compress and hold up weight). I would trust your own perceptions though much more than technical specifications or information when you are testing mattresses locally.
This could be because they were each on a different base, because one mattress was new and one was broken in, or it could be subjective perceptions. Most people have had the experience of testing a mattress earlier in the day and then testing other mattresses and going back and re-testing their first choices and being very surprised that the mattress felt very different because the subjective memory of how a mattress “feels” can vary with time and circumstances or even with “mood”.
Exchange policies can be an important part of value for people who aren’t confident about the suitability of their mattress choice and is one of the factors in each person’s personal value equation. OMF has ant exchange policy you can see in post #4 here but if you wanted a latex mattress there would only be one other option available (although you could also add a topper to it).
Phoenix