Wear indicators are a separate thing from the pads .... they are not part of the pad.
I didn't say the wear indicator was part of the pad?
The terminal pin of the wear indicator cable snap fits into the bore in the bush that's factory pressed into the pad backplate. Usually bronze (or is it brass) on genuine GM pads. The bush that also acts as the pivot for the spring.
If the bush is pressed in from the wrong side, as
robson indicated above, then the wear indicator won't fit. It'll rattle about.
Robson asked if it was a manufacturing fault and I was commenting on that. More likely that the pads in the box were intended for some other vehicle that uses the same Lucas Girling caliper, but maybe has no wear indicator. So the parts actually in the box are incorrect for the indicated application as opposed to incorrectly manufactured.