If I've ever had one of those head-slapping moments,finding out about this little hole is one of them. It is only a coincidental appearance on the bridge plate, and its purpose is essential to cutting the dovetail neck joint on the carriage apparatus that's used in that manufacturing step. If my technological skills don't fail me, there should be a picture of that jig. The variety of positions we see in the relation of this hole to the bridge pin holes are all about the proper placement of the bridge on the top to dial in the exact intonation on each individual guitar. The bridge might necessarily move forward or back a smidge, to get the intonation spot-on. Following the install and gluing/drying of the bridge, the pin holes are drilled. That is why we see some closer to this hole than others. Has everything to do with intonation, and perhaps this little hole oddity contributes to the individual personality we all seem to experience in different Gibsons. It is apparent that even though this hole may be close to pin holes, it would probably be very rare to see a pin hole that wasn't completely surrounded by at lest some Maple. And the glue that is used to affix the spruce plug to the top fills that hole with a material, that to my observation anyway, is at least as hard and resilient as the Maple bridgeplate itself.
As i understand from observing all of these steps, the location holes are drilled in the guitar tops (there's one up under your fingerboard too) After numerous steps, these tops are affixed to bodies, destined to be mounted and clamped to the jig which essentially creates the recess for the dovetail neck joint. Further down the assembly both of the locater holes are plugged with spruce (and glue). Necks are fitted, binding is installed etc etc, and then the guitar goes to be measured for scale, and intonation, and the bridge is installed.
The hole is essential to the precise dovetail neck joint. In later steps, the hole is filled with spruce, and later covered up by the bridge. And it is the placement of this bridge fundamental to intonation, which positions those pinholes closer to, or further back from that locater plug.
I believe it is important to me to have a precise neck joint, and good fundamental intonation, and an invisible locater hole from the drivers side of the guitar. Probably way more important than poking my head under the hood and fretting about that hole. In my estimation, it is a very inconsequential thing. The ball ends of strings will probably weardown the Maple faster than they would that epoxy. I an't worried no more !
If you select this picture, it should lead you to my Photobucket place, where you should be able to see the other jig, and a couple more shots of the life of this hole.