I believe AS is still on Sabre. On AA Sabre, the "row" X seats are unused FA (cabin) jumpseats and the W seats are the cockpit jumpseats.
To date myself, AA's 727-200 had 2 cockpit and 5 cabin jumpseats. The FAA minimum cabin crew was 3. Depending on flight load and/or if a meal was served in coach (I'm really dating myself now), the FA Union contract could call for a cabin crew of 4 or 5.
The cabin jumpseats are actual crewed positions, even when not required by FAA/Union. You must be trained as an FA to be assigned one as your seat. Commuting FA's flying on a non-rev pass will be assigned these seats if the cabin is full. Uniform not required, but many don't change clothes when going to/from work. If you've ever seen an FA literally sit in the jumpseat the entire trip, it could've been an off duty pass rider.
The cockpit jumpseats are "spare" seats. They have no operational need beyond somebody (airline's Check Airman/Instructor or FAA) wanting to monitor the pilot(s). In my airline days, the FAA rule was that any airline employee could ride there, but AA's (and I'd assume most airline's) policy restricted the seats to pilots or employees who had (either long term or "one time") authority. As a DFW Operations and later SOC (System Operations Control .. the system wide "nerve center" near HDQ) employee, I've ridden "W" on 4 flights (what a difference between the 727 and 757 !!!).