Did the factory drill my bridge holes too big?

The holes are probably the right size for the kit bridge, so it’s likely to be a mismatch in specs between fully metric Asian hardware and hardware designed to replace US imperial hardware. Buying this stuff to retrofit can be a minefield! Presumably you’ve got some digital callipers. If so, measure the kit and the Gotoh inserts and see how much they vary by. Probably not a lot, but enough. The kit inserts will have an M8 thread, and it looks like the Gotoh posts do too. If so, I’d use the kit inserts with the Gotoh posts. Otherwise its a question of plugging the holes, and re-drilling with true 11mm hole.

If you look at Gotoh bridges, you’ll see the ones they make to replace Epiphone bridges (Asian made) have a 11.3mm base width to the insert, as opposed to the 11.1ish mm of the ones for US Gibsons (which I’d guess have 7/16” holes). It’s a small but important difference, as you’ve found out. Unless I’m drilling the holes myself, I always get the Epiphone fitting parts in order to work with the kits.

As I’ve said before, the forces on the bridge are downwards and slightly forwards, so there’s normally nothing pulling the bridge and inserts upwards. So the inserts need to be in firmly to stop wobble and keep the bridge in the right place, but they don’t need to be gripped quite as firmly as the stoptail inserts (though it doesn’t hurt). Just don’t forget to fit the bridge ground wire before fitting the inserts properly.