Put simply, he doesn't know what he's talking about. He says the form he is looking at is the official tax return of the WTBS, and shows its investments. It isn't and it doesn't. This is a tax return for a charitable trust, which is a separate entity created with somebody else's money. In this case it's the Henrietta Riley trust. The money invested is hers. Under US tax law, the beneficiary of such a trust has NO say in the management of the trust. It is managed by a trust company and regulated by the legal instructions of the person who established the trust, in this case Ms. Riley.
There are large issues for which the Watchtower needs to be held accountable. This isn't one of them, and harping on it obscures the real issues and gives JW's that choose not to see facts a good excuse not to look at real information about real problems.