I suspect this has more to do with reducing short cutting through the community than it does safety. There's a fair number of drivers who will turn up one of the streets by the curling club and then take 2nd ave or 4th ave over to 10st in order to avoid the Memorial and 10st intersection. It saves a lot of time, and perhaps they think that a 30 km/hr speed limit will reduce that time savings and reduce the traffic.
(That or raise money for the police department by parking a full time photo radar van on 2nd ave
).