It is not so clear if it possible to read set state of GPIO pin what is configured as output.
I can configure Pin to output and set it to High level. But if due external shortcut, this pin is connected to ground,
by use PIN register I will read 0 state even I set it to 1.
From what GPIO register I can read output value if pin what was really set by software, but not real state what is on that pin ( e.g. as it read if it input ?)