USB2.0 vs USB 3.0

Question

I have read that USB 3.0 can provide 900mA of current where as USB 2.0 can provide 500mA both at 5V.

I understand in USB 2.0 there are 4 connections, Vcc, Data+, Data- and GND. In USB 3.0 there are these pins plus Tx+, Tx-, Rx+, Rx- and GND (i.e. USB 3.0 had more data lines/ data carrying capacity).

How can USB 3.0 carry a higher current despite not possessing any extra power lines? Is it possible that more current can be supplied through the additional data lines (Tx+, Tx-, Rx+, Rx-) if, for example, the USB cable is only being used for charging?

Answer 1

You are reading the specifications.

It just means those are the values a port must support.

You do have USB 2.0 ports that can output 1A or 2A but the specs do not require it.

It is just handy if you have a USB hard drive which requires more than 0.5A or portable device that can charge at more than 1A.

Surely the PCB wiring and any overcurrent or shor circuit protection is designed respectively to be able to carry that amount of current without too much voltage drop.