Question: Why are behentrimonium methosulfate and cetearyl written together?

Angel wrote to me to ask: Why are behentrimonium methosulfate and cetearyl alcohol often written together as though they are a compound solution?  I understand your explanation of why the cetearyl alcohol is used with the behentrimonium methosulfate in hair conditioners.  But is there a reason why I’ve found the two written together as one compound…