Hi AdamSF,
I think that the person you were talking to is mixing up several “apples and oranges” issues and giving you some misleading information.
The foundation you purchased would certainly be “breathable enough” and very suitable for a latex mattress.
I believe that the fire retardant they use is an inherent fire barrier which is also “safe” and non toxic. It sounds like the salesperson you were talking with may have been trying to “find reasons” to try and convince you to buy their foundation even though the reasons they provided were somewhat misleading.
It’s also true that a wool quilted foundation would probably be “more breathable” and regulate moisture better than just a cotton cover but the benefits of this on the bottom of a mattress may not justify the higher price unless someone was only interested in using natural materials in their mattress and foundation. Even a solid surface foundation that doesn’t breathe at all would generally be OK for a latex mattress as long as there weren’t other risk factors that would increase the chance of mold or mildew (see post #10 here).
I wonder if he would also tell you that an adjustable foundation with a solid surface that doesn’t “breathe” at all wasn’t suitable for your mattress if you wanted to use one under your mattress?
Phoenix