Nobody knows how stable it is or isnt - it might not have settled. There could be damage internally, walls and/or ceilings collapsed, blockages and debris, sharp bits of metal.
The other practical problem may well be there are no mooring balls on or near it (sand chute the exception).
Its a tourist attraction - from a risk assessment point of view it makes perfect sense to close the attraction until it can be properly evaluated and if needed, brought back up to spec.
This isn't a "natural" wreck put down by war or weather. Its a sterilised tourist attraction put down for that reason by a government body so the standards are different.