BPI-R3 unidentified cutout in case

On the side of the R3 case, immediately to the right of the cutout for accessing the DIP switches, there is another rectangular opening. What is this intended for?

At present I have the wires for the TTL to USB adapter poked through it so I have access to a console.

Is there a part, perhaps third party, that can slot into this opening for a USB port to accommodate the TTL connection? Or som either purpose to expose say GPIO connections?

It seems odd for it to be there unexplained given the very high quality standard of construction of everything else and how it all fits together.

Thanks.

See:

Assembled BPI-R4 case share - Banana Pi Router design / BPI-R4(MT7988) - banana pi single board computer open source project official forum BPI team