All the people who have access to booking information can see the loads and all "sensitive" data. All the people means almost everybody but the pilots and cabin crew. This is just a way to punish us and it does not have any other explanation (indians selling info, skywards passengers and so on).
Punish us for what? I dont know, but that's clearly The reason behind this decision.
Capetonian, that is not such a secret. Just get closer to someone behind a ck-in desk at the airport (even abroad) and you get all the magic numbers.