It's jack access.
Common on Gibsons.
Strats have face mounted jacks with a jack plate that covers a hole large enough to accommodate the jack.
Tele's have side mounted jacks but again with a jack plate covering a larger hole to pull the jack thru.
This thing has a barrel jack with a collar which means the jack doesn't fit thru the hole / is held in place from the backside.
Some companies handle it with a large pick guard so you can access it from the face. Pick guard here is not big enough for that.
Conclusion, jack and associated wiring access.
