Ok, maybe explain how I'm wrong, because most wax/shatter recipes I've seen explain decarbing your herb not your finished product. The only reason ive heard for heating shatter has been to melt it, dab it, or for removing any leftover solvent.
Wait, why are you telling him to decarb a finished product. Correct me if I'm wrong but... Shatter should be made from decarboxylated flower as it is. And as for fat, the gelatin in the recipe should work as gelatin binds with fat.