Pearson International Airport does not close. It operates 24 hours a day.
Here is the reality, direct from the airport itself;
Is Toronto Pearson closed at night?
Toronto Pearson is open 24/7/365. Our night operations are a mix of cargo and passenger services.
The airport manages a Night Flight Restriction Program to manage the impact of aircraft noise during restricted hours (12:30-6:30 a.m.). Transport Canada has imposed annual limits on the total number of night flights at Toronto Pearson to ensure that flights during the restricted period remain proportionate to overall traffic levels.
The GTAA uses a night preferential runway system from midnight to 6:30 a.m. using flight paths that impact the fewest people. The order of priority for preferential runways is: Runway 23, 33R and 24R for departures, and Runway 05, 15L and 06L for arrivals.
As per the airport statement that it has both both passenger and cargo operations 24/7 this means that the airport does not close "practically" nor "technically".
Any statement to the contrary is therefore not correct.