Hrm, you might be right. My usual reporterese-to-actual-reality heuristic gave me "They said there was some prior art that wasn't noted at the time of the filin

Hrm, you might be right. My usual reporterese-to-actual-reality heuristic gave me "They said there was some prior art that wasn't noted at the time of the filing," and that is a commonplace situation — but your interpretation makes sense as well. My bad for autopiloting it.