Well, I definitely didn't remove one from the '88 I did the 302HO swap in

I wonder if this is a Canadian/American truck difference? Though I know the US Mustangs didn't get them (EEC-IV).
Regarding the linked thread, the fact the truck lower he got also didn't have the provision for the knock sensor has me thinking there's something else in play here, as clearly some didn't have them. It could be that California trucks got them, or maybe he got a Canadian lower manifold? Or maybe Ford deleted them later?
Really weird that the cars would be SEFI and no knock sensor but the US trucks were primitive batch fire but had a knock sensor, lol.