Yes, I think there is a clear explanation here. I'd even be reluctant to suggest paying for that seat row, due to umpteen changes that could happen, including you ending up on AA metal. At OLCI you may be able to get the seat you want for free anyway. Sometimes the BA system doesn't pick up Sapphire status, since your booking is actually hosted on a separate system and the interface has only slightly evolved from two tin cans on a piece of string. But usually a call to BA., quoting your AAdvantage number, will resolve issues there. But in this case it is essentially an Emerald perk.

Welcome to Flyertalk and welcome to the BA forum lewisid69.