What is ironic is that if that same drop cord is connected permanently then it is no longer a drop cord but a pendant and is now legal.
III. Required Outlets
210.50 General. Receptacle outlets shall be installed as
specified in 210.52 through 210.63.
(A) Cord Pendants.
A cord connector that is supplied by a
permanently connected cord pendant shall be considered a
receptacle outlet.
(B) Cord Connections.
A receptacle outlet shall be installed
wherever flexible cords with attachment plugs are
used. Where flexible cords are permitted to be permanently
connected, receptacles shall be permitted to be omitted for
such cords.