(I saw this the other day and I forgot to verify.)
I saw a picture somewhere of that hand clutch but I don't remember where.
I believe if you look the newer style pedal there is a second somewhat smaller hole above where the clutch rod hooks into the foot pedal.
I am under the impression that is where that hand clutch hooks in and the foot pedal remains in service. I had seen that hole in the pedal before and the picture seemed to explain its purpose.
I will have to look but I don't think the fleet lines have this extra hole. I have seen the newer pedal on the older tractors so maybe you had to change it to use the hand clutch on the fleet lines.
RT (my 2 cents.)