The WTB&TS of PA is simply a large multi-national organization that needs places to invest its liquid assets. K2 Advisors is required to disclose any party with "control" over the fund. The SEC views 10%+ ownership of the fund's assets as "control", or if the fund agreement specifically allows certain shareholders to hire/fire the investment manager (hence "control").
Based on this Form D filing, the fund had an assigned value of $500,000,000. As of the Form D filing, WTB&TS was the sole investor, having purchased $40,000,000. WTB&TS, due to its size, meets the definition of an "Accredited Investor". The Appendix discloses that the WT was the sole accredited investor at the time, and there were no non-accredited investors that had invested in the fund-- therefore the sole investor.
These funds certainly offer favorable tax treatment, but nothing illegal. Any gains on this investment would still be reported on the WT's U.S. tax filings.