USB cables combining shield and power ground conductor
Considering that shielding the data wires is desirable to keep interference away, and considering that shielding is virtually always grounded, it should come as no surprise to find the ground conductor and the overall shield combined. In fact, in  most kinds of shielded cables, that is common practice.

There are rather complex "handshaking" protocols established for USB peripherals to negotiate for how much power they require from the host.  And for "dumb" hosts like simple chargers, Apple has a scheme for setting the D+ and D- pins at fixed voltages to indicate how much current is available.  For example...