I'm inferring that the OP didn't check on the LATAM site as he references an AA printout of the seat assignments.
I've had several occassions where, for whatever reason, the operating carriers seat assignments don't match what AA or the booking airlines reservation shows. They may match initially, but later changes often don't get reflected. Sometimes, the ticket isn't even valid, even though AA said it was. Always check on the operating carriers site.
Not to mean that the OP is incorrect. But it's not the most likely explanation if they didn't check on the op's site (and recheck).