Maybe some factory used a brittle finish that was prone to cracking around the neck plate so they used the plastic thingy to try and prevent that. But as McCreed, says, it's totally unnecessary and you just don't fit it. The basic chrome neck plate otherwise seems identical to what you'd get on a Squier or Mexican Fender.

By the time you get a few coats of finish on the headstock, you'll find the press-in bushings will seat a lot more firmly (you may even need to sand the finish back a bit to get them in!), but I'd still run a bit of wood glue around the edges of the bushing first. The bushing is actually quite important in the operation of the tuner, it's not just there for decoration. The string tension will pull the post forward slightly, so it should rest against the edge of the bushing. This significantly reduces the load that would otherwise all act on the base of the tuner, reducing wear over time and allowing smoother operation.