Actually the 'FD commands' immediately available after an A/P disconnect under normal circumstances are intended to be valid. That is how you would normally transition to hand flying the aircraft.
A/P disconnect was not the cause of any erroneous or misleading FD commands. When the A/P disconnects as a result of 2 or more ADR's going on the 'fritz', the FD's are automatically removed, but the buttons NOT automatically deselected (even the light in the button stays on).
It's the intermittent default FD commands that that 'pop up' in a UAS situation like this that are not to be blindly trusted. That is why, in the interest of avoiding this source of confusion, the FD's are to be deselected manually in an UAS situation.
There are other situations, e.g. PRM breakouts, where the FD's are deselected, because the existing or default vertical guidance may not be compatible with the PRM breakout procedural requirements. Has nothing to do with the A/P being disconnected. Has to do with being a pilot.
This is not your "grandfather's" FD-109.