If GWS played Thursday last week and Geelong played Friday, why isn't the GWS game on Friday and Geelong on Saturday?
Winner of Geelong v Sydney plays Adelaide, therefore to avoid a 6 day break, they give that game the Friday Night.
From this, no teams have any 6 day breaks leading into the Grand Final except Sydney.
From Week 3 (Due to the bye, 1st weeks game doesn't matter)
Adelaide Friday --> Saturday
Richmond Saturday --> Saturday
From Week 1
Geelong Friday-->Friday-->Friday-->Saturday
Sydney Saturday-->Friday-->Friday-->Saturday
GWS Thursday-->Saturday-->Saturday-->Saturday
WCE Saturday-->Saturday-->Saturday-->Saturday
As you can see, Sydney would have the 6 day break leading into the Semi or the Prelim. As the Prelim is seen as the more important game, it is given the 7 day break. Either/or, it's the only one this entire finals series.

