Koga rear rack cross-member attachment holes

Transistor

Finding my (electric) wheels
Jun 2, 2012
6
3
43428

My Koga E-lement has a battery pack version of this rear rack. There are four holes (green) and four slots (yellow) running front to back in two of the cross-members.

Does anyone know what they're for? Are they fastener locations for paniers?

Thanks.