We are to disconnect autobrakes via manual braking, not using the switch. I believe that is still required across all fleets at our company. I can understand directing the PM to change the auto brake setting during the approach because of unanticipated conditions.
I can not understand doing that on the runway. So the Captain is landing and now decides to: take his eyes off the runway, look over to the autobrake panel, take his right hand off the TL’s and reach across the cockpit to deselect, select, or increase the AB setting. Or one may say, well no, he directs his FO to do the action. So now that FO is presented with a command from the Captain he most likely has never encountered nor anticipated and is to complete during a critical phase.
I can easily imagine a hundred things which could go wrong. Isn’t our job to manage the threats inherent in our occupation not add to them?