A loadsheet is the biggest piece of fiction in aviation.I have flown the majority of Airbus types in many varied types of operation around the world and the aircraft always comes out over what you think it weighs.This can be in the order of 2T for an A320 on a charter back from the Eastern Med to almost 10T over on an A300 on the hadj.Unless you personally weigh every person and every bag you will never know what the true weight is.
Even with the best loading team in the world an aircraft is usually heavier than the loadsheet.It makes me laugh how some people try for theoretical accuracy in obtaining a cg position based on the notional weight.One fleet manager told me on the A320, as long as the trim is in the green band on take-off the aircraft is flyable.
I have never seen an aircraft that is below the weight on the loadsheet.The hadj is simply organised chaos with operational standards directly proportional to the country of registration of the aircraft.If you tried for absolute accuracy you would never leave the KSA.The problem is usually due to exceeding max zero fuel , a structural limit rather than a performance limit.
The culture is to load up any available space regardless of any limit ever imagined by engineers in Seattle or Toulouse.Those of us with some pretence at integrity will do their best to limit this but many other operators will gladly accept this situation in their antique aircraft and hope that the forces of natre never catch up with them!