What do you make of this diagram on the speed control page of the 68 Electrical assembly manual?
Possibly for the other supplier and ford choose to illustrate that one on that page. You'll notice that the switch as illustrated in the assembly manual is not included in the kit as shown.
Bottom line is that the drawing suggest IMHO that someone at some point designed the pedal with the hole for some purpose (likely this one application) though we don't know if the purpose was dropped or supplier changed their design of the cruise control parts and installation. We know that each drawing that Jim put in the reprinted manual is a snap shot in time but we don't know what was done before nor after that point in time.
Could you provide the revision date from that page?
Date on the box the kit came from was late in the 68 production year Believe it was May 68 but will double check and correct if needed