Hi JCLARE,
It’s not uncommon at all for different manufacturers to make different recommendations or suggestions and this can often be as much the norm as the exception. This could be because of differences between the specific materials and components in each mattress (including the thickness, type, and blend of the latex layers and the type of cover and quilting), differences in “word” ratings for firmness, or most often because of genuine differences in opinions between different people about which mattress will be the best “match” for any specific person. Online recommendations or suggestions are as much an art as a science and for most people there won’t be a specific “best” mattress and there will be a range of different mattress designs that will be a good match for their body types, sleeping positions, and preferences. The range of mattresses that will be suitable for each person will also depend on their sensitivity where they are in the range between “princess and the pea” and "I can sleep on anything. Post #8 here discussed all of this in much more detail.
There is more about the different ways to choose a mattress that is the best “match” for any specific person and how to reduce the risks involved with each of them in post #2 here.
There is also more about the most important parts of the “value” of a mattress purchase that can help you make more meaningful comparisons between different mattresses or manufacturers/retailers in post #13 here.
Phoenix