Toronto is the same. I sure wish more international airports with high US outbound traffic did this.
Most major Canadian airports have this: Montreal, Calgary, and Vancouver for sure, and I believe a few others.
Globally more and more airports are offering this service. Abu Dhabi has for about a year, and I just read that an agreement has been reached for Stockholm to get it.
Several Canadian airports have US Customs (actual US customs employees) clearing you before departure, so it does not have to be done on arrival.
If you are arriving in the USA from anywhere else then carrying on inside the USA, odds are you go through customs on arrival. Therefore, you need to be with your bag during the transition from international to domestic. (Just so you can’t claim “that wasn’t my bag” if questions arise about its contents). If you are flying from the USA to overseas, you don’t need your bags until you arrive overseas and go through their customs.
I once went to Australia through LAX from Vancouver, and my luggage went straight through since I was not stopping on US soil. The same coming back, except we DID spend time on US soil. Our bags transshipped, but we took the 4-hour layover to catch the shuttle bus to the parking lot and then walk (!!) from there to In-And-Out Burger. I assume they did not make us retrieve our bags because then we did not have the opportunity to take anything out and leave it in the USA duty free, or partake of packed illegal substances. (Although if they’d caught use toting Kinder Surprises in our luggage I’m sure they could still charge us…)