This tax return is not for the Watchtower Bible and Tract Society. It is for a trust, of which the Watchtower is a beneficiary. I have some personal experience with trusts, the following is based on that knowledge.
A trust is a separate legal entity over which a trustee, in this case the WTBS, has no control. The trust is managed by a Trust Officer who is required by law to whatever the trust document tells him to do with the money. The beneficiary can, I suppose make suggestions, I don't believe the trust officer has to follow them; he certainly doesn't if they conflict with what is in the trust document.
I googled the address on the Form 990. It is for the trust department of a Comerica Bank in Detroit. This is just one of who knows how many trusts they handle. Comerica is a large financial services corp, I can't see any direct connection to the WTBS.
So what we have here is some rich lady who set up a trust fund, which is directed to make money for the WTBS, an operation over which the WTBS has no control.