I went and poked my head into a A320 to compare, and they are identical to the A380 sidestick.
The A380 has the thumb indent, same as A320.
edit
Good spot Chris...
It is not on any of the 8 A380's I've flown. ???
QF A380's are the same as MSN01
Photos: Airbus A380-841 Aircraft Pictures | !!!!!!!!!!!!!!
Must be a 'Desert Drivers' option, for those who suffer from 'Camel Thumb'.