On board the purser told me the delay was caused by a technical issue. And in fact I was able to verify that the ac was supposed to fly in the day before from Afrika, but then remained on the ground there for the night and only flew back to CDG with 10+ hr delay.
We departed CDG with close to 5 hrs delay and touched down at like the 3:55 delay mark. Long taxi, on stand 3:58. Doors disarmed at 3:59 delay. Doors opened at 4:04 hr delay compared to the original arrival time. Actual arrival time is calculated from door opening time right?