Beautiful horn on that one!
My understanding as to why GEC will not work with buffalo horn is the multitude of problems that occurred when they have used it in the past. If the horn has not been properly stored/seasoned(?), it is prone to warping and shrinkage and due to that, GEC experienced a lot of returns of knives that developed gaps and what not.
My experience with the material, both with my knives and what I have read from others, is that it is one of the more finicky cover materials and can be affected greatly by the environment it is owned/used in. I live in a rather wet environment so Buffalo Horn does pretty well but there are some here who live in very dry climates and they have experienced significant shrinkage.
I would love to own a horn clad knife made by GEC and for a moment, i got my hopes up with this upcoming run of 85s. However, I can understand GEC's stance in regards to using it on future runs.