The chauffeur is watching the flight before it lands and is in the terminal building by the time you reach the baggage hall. They park in the garage rather than working the arrivals roadway, which means the meeting point is fixed and indoors: you walk out through the arrivals doors and they are standing there, not three lanes away with a traffic officer moving them along.
That distinction matters more at Pearson than at most airports. The arrivals level is actively managed, vehicles cannot linger, and the alternative arrangement — a phone call, a description of a black car, and a lap of the terminal loop — is exactly the experience people are paying to avoid after a nine-hour flight.
Luggage is taken from you at the doors and loaded by the chauffeur. From there it is a short walk to the garage rather than a wait at the curb, and the vehicle is already at a sensible temperature.