WLM has two operational F/A-18 squadrons; 3 and 77 based there. (Plus the 2 Sqn Wedgetails.) I suspect one reason that they take up so much airspace is because of their training purposes. 2OCU do most of the Hawk to F/A-18 conversion training there. That includes refuelling from KC-30 aircraft and now tactical stuff with the Wedgetails.
But I do agree that the restrictions on the eastern side GA route are well over the top.