I think it may have something to do with the feel rather than actual volume change. the 08 boards to me felt big and i would have used one size down compared to the previous s-types.
The new 09's are different in they feel more alive, easier to gybe and slightly racier, and this could be seen to "feel" smaller to some.
I am 75 kgs and would use the 101 for 5.5 to 7.5 sailing in consistent wind but the 111 would be preffered in 70 to 7.5 weather. the 122 feels great but too big for anything other than flat water for me.
for an 80 kg guy up to 7.5 the f111 would be a great choice and it is definately easier to sail.