Curious Cutout; What Optional Accessory Goes Here?!

I recently got the drill/driving kit from Bridge City Toolworks (no link to the kit since it sold out).

It's a high-quality kit with bits and drivers for hex shafts (read: no slipping in a keyless chuck!) that was specially put together.  Here you see one layer of the parts.  The majority of the bits actually come from Montana Brand Tools so you can pick these up separately.

Now, Bridge City always comes up with this clever packaging with a space for each thing (the CS-12v2 packaging rocks in this case, but that's another day).

So, while digging for a self-centering pilot bit, I noticed a cut-out with nothing in it.  Give it a look.

Here's a closer peek.

Now, I have to wonder what optional accessory this cut-out is for.  If the ladies who ordered this kit could chime in... Bridge City knew I already had one.