No, the report isn't "a bit thin".
If anything, the report is too harsh on the controller and not harsh enough on AsA.
I've regularly been in the circuit at YMMB both before and after the date of the accident and the controllers have to work their backsides off; you can hear it in their voices sometimes.
They are especially busy when the bigger schools start a new class and all of a sudden you have four or Five aircraft with students flying circuits for the first time, often not that familiar with voice procedure and a bit of an accent. Add in a Third solo and a couple of arriving aircraft, say one asking for circuits on arrival and another asking for a glide approach, then perhaps an IFR departure and it can get very busy very quickly with no warning. That is why you now have to ask for start clearance for the circuit these days.
I've heard a controller say "which Cessna are you? Waggle your wings!" when a tongue tied student can't explain which Cessna he is (turning downwind, early downwind, mid downwind, late downwind, etc.) I've also heard a controller chastise a student who independently decided that instead of going around, he would try an orbit on final to get better separation.
When I start to hear the controllers loading up like that I do a full stop to avoid adding to their workload - which is still substantial today with class D.
Go easy on the controllers they do a fantastic job, it's AsA who should have been looking at the increasing workload on their staff because since in 2008 the whole overseas student thing was in full swing at YMMB and the workload had increased considerably. AsA should have been proactive, not reactive.
P.S. The pilot of UPY isn't and won't be the only one to confuse 31L and 35L, I did it as a student pilot by following a Metroliner on final as instructed by the tower, only the Metroliner mistakenly landed on 31 instead of 35, fortunately without incident. The controllers warned me off in time. I think the pilot had tea and bikkies with the controllers after that.