Considering the path-planning requirements I would be absolutely shocked if Autopilot wasn't build history models and estimated paths for objects around the vehicle (other cars etc).
I expect what happened was that they trained their NNs for improved detection in one area but unknowingly reduced it in another. Perhaps now it can detect tricycles 99% but road barriers went down to only 30%. Having worked with NNs it's very common to see gains in one domain which come at a cost of reduced performance in another.
Barriers are a pretty big part of driving on roads and highways and the only reason it would have been unknowingly reduced would be if they just weren’t testing the NN against data with them.