No I think its a false narrative because I'm a retired accountant and financial manager. I have no doubt some CO told you this story. I have lots of doubts that he knows what he's talking about.
The described activities are not money laundering. Money laundering is used to disguise the fact that money is made illegally and/or to avoid taxes. What illegal activity is the WTBS engaged in that requires hiding the proceeds? Selling Kingdom halls is not illegal, its also impossible to hide the money since its a publically recorded transaction. The WTBS is a religious organization, as such it doesn't pay taxes on most activities, so they don't need to do that either.
As I said, they could loose everything, why take the chance? I don't see a reward that justifies the risk of moving money around clandestinly. If I was on the GB and wanted to hide money earned from some nefarious activity (the definition of "money laundering", I'd just have somebody dump it in the donation boxes at a convention. It then becomes "cash donations" and its clean as a whistle.