Contacts on the back panel (battery cover) of the Xperia Z3+/Z4

I opened the back panel of my Z3+/Z4 to replace the battery, which was easy enough. I wanted to also replace the back panel (already bought one), but realized the new back panel/housing I have does not have those two copper(?) contacts on the upper right side of the back panel (when you’re facing it). They look like they align with a couple contacts on the inside of the device. My device turns on now and the battery is fine, but I’m currently still using the old back panel without any adhesive (a case is holding the phone together). What are those copper contacts on the back panel? Are they important, or could I just use my new back panel that doesn’t have those contacts? (Some devices from the older Z lineup don’t have those contacts, based on the teardowns I’ve watched.)