I did look around today, I did not see any $630 roundtrip. It must be double that price. The lowest from YYZ is by breaking YYZ-ORD-YYZ then ORD-SIN-ORD on the Amazing Asia Fall Sale.
But, if you want to maximize your miles, you may consider JFK-LAX-SIN-NRT-SFO-JFK on the V-fares 6-days min Amazing Asia Fall Sale for USD 1,010 and some change inclusive taxes. Europe to JFK should be very competitive I suppose.