I have also noticed a few circuits like this one:
https://nurdspace.nl/Arduino_on_a_breadboard
and this one:
http://www.jameco.com/Jameco/workshop/JamecoBuilds/arduinocircuit.html
Where pin 21 (ARef) gets connected to +5v. Is this necessary or could this make a difference? The original circuit I posted from the official Arduino site did not connect this pin to +5v. It only illustrated the pins on either side (22, 20) to be connected to Ground and +5v respectively.