Whether or not a supplier or manufacturer has a return policy on products is something you’d always want to consider in importance as part of your personal value equation.
Unless you are buying the exact same foam produced by the same supplier to the same specifications, there will always be some differences in comfort. Additionally, you’d need to test the exact same foams in the exact same configurations using the exact same coverings to achieve a sameness in feel. And latex will soften slightly with initial use, but the change isn’t as dramatic as with polyfoam.