Very likely this is normal. The battery is "7.4V" which means really it is two "3.7V nominal/average voltage" in series. A balance wire for a 2S battery only has 3 wires one on GND side one in between the cells and one after the second cell so it can measure and control current in or out of the individual cells via those three wires/connections. Your guess is as good as mine regarding what the other 4 connection points are being used for, it might just be they are splitting current across pairs of pins and could be the charger uses the extra pin for a temp sense resistor in the battery as extra protection to turn off if things get extra hot (again a guess). Maybe someone with this or similar can verify but doesn't sound like something that would pass any sort of QC or break in shipping.
Yeah, I don't think such a thing would happen in shipping. It might have been a return item wherein the earlier purchaser manhandled it and pushed the pin through the case somehow, but it didn't bear any marks that hinted at this. It looked pristine. QA? Who really knows about that?
I ask because the controller display stubbornly indicated zero level battery for the copter, in spite of a full charge. It also failed to function in other ways but clearly was operating at some level with flashing lights, etc. After posting this inquiry I found a video of the HS720 model - presumably its successor and possibly of similar design - which exposed the pins. The copter in the vid clearly has all 7 pins. So I sent mine back to Amazon. I just ordered the HS720. Maybe I'll have better luck.