The institutions follow the rules. They dinner necessarily overly follow the rules or run up costs for filings they do not need to make. But most likely they are not buying.
In addition, hedge funds are NOT public and live to do things secretly, so it is right up their alley to not file. Same with family funds. Why would they publicize if they do not need to do so otherwise?
Hedge funds are not mutual funds. Neither are family funds. They try to limit disclosures not maximize them. They try to limit their regulatory overhead, not over do it.
Plus you have offshore family funds and hedge funds that would not want to file at all as well. In fact I traced one short who I think also may have traded NWBO years ago to a Hong Kong based big family fund office. I think he was always a short trader though, so I doubt he ever held a position that would need to be disclosed. The fund’s position is always as a “shareholder advocate” and he always was negative. Had some connections to big US banks and US mutual fund complexes, from his past work and maybe some ongoing relationships. So you never know.