I managed to locate information about the OVRD light after finding a main flight manual it is possible to search in,
https://info.publicintelligence.net/HAF-F16.pdf. Previously I only had a scanned version. Below are extracts from the manual and the OVRD light is indeed related to the D model aircraft and not to the manual pitch selection. You can find the related sections in the manual by searching 'ovrd'

NOSEWHEEL STEERING (NWS) SYSTEM
Either cockpit can control the NWS. Control is
accomplished by means of an NWS control button/
indicator located in both cockpits just aft of the stick.
Depressing the button/indicator transfers control of
the NWS; the indicator illuminates green in the
cockpit which has control. Control then remains in
that cockpit even if the engine is shut down and/or
electrical power is removed. NWS can only be
engaged and operated from the cockpit which has
control. When NWS is selected, the NWS light
illuminates green in both cockpits. The aft stick
paddle switch allows immediate override of the
forward cockpit if the STICK CONTROL switch on
the TEST switch panel is in AFT; the NWS control
button/indicator in the aft cockpit and OVRD light
illuminates. The front cockpit paddle switch cannot
override the aft cockpit regardless of the position of
the STICK CONTROL switch. With the AIR
REFUEL switch in OPEN, NWS can be engaged or
disengaged from either cockpit without using the
paddle switch regardless of which cockpit has control.
STICK CONTROL OPERATION
With the STICK CONTROL switch in FWD, the stick
indicator displays the word FWD. Depressing the
forward cockpit paddle switch locks out the rear
cockpit stick, rudder, and MPO commands. The
OVRD light in both cockpits illuminates indicating
override is activated. Depressing the rear cockpit
paddle switch has no effect on the forward cockpit
controls.
With the STICK CONTROL switch in AFT, the stick
indicator displays the word AFT. Depressing the
rear cockpit paddle switch, PX III with the ASIU
switch OFF or the ASIU STICK CONT switch in
FLIGHT, locks out the forward cockpit stick, rudder,
and MPO commands and transfers control of NWS to
the rear cockpit. The OVRD light in both cockpits
illuminates, indicating override is activated. De
pressing the forward cockpit paddle switch has no
effect on the rear cockpit controls.
Stick OVRD Lights D
Refer to figure 1-90. The stick OVRD lights, located
on the forward and rear cockpit instrument panels,
illuminate when the paddle switch is used to take
control.