It would be interesting to see how much AC's on-time performance would improve if they set block times the same as the airlines above them on the list.

OTP is relative to the schedule the Airline publishes so for example, if a UA + AC flight leave at the same time from EWR to YUL, and they both land 1h55m later, the AC flight is 'late' while the UA flight is 'on-time' as AC schedules the route at 1h36 mins and UA schedules it at 1h48 mins. The AC flight is 19 mins past schedule (late) while the UA flight is 7 mins past schedule (on-time).