it will take almost one hour for its maximum load of 853 passengers to board
This sounds almost ridiculous. Then you work it out and find it is ridiculous.
A380 will always use double deck jetways, so 426 each door. If it takes an hour that's just 7 pax per minute. Somehow I think we normally achieve quite a bit more than that. bear in mind that an 853-pax load implies all high density seating, no premium "relaxed" boarding needed.
Existing 747s often hold 426 pax and do single door boarding. And yes, they take much less than an hour to do it.