One famous person who did this was Larry Ellison using Oracle shares. This almost caused a problem for him in the 90s due to the stock dropping in value:
https://www.sfgate.com/news/article/Inside-look-at-a-billion...
https://www.sfgate.com/news/article/Inside-look-at-a-billion...
His advisor did his job by warning that this could go wrong if Oracle stock dropped massively. But it never dropped that far, so he was fine.
And most ultra-rich that own lots of shares of large publicly-traded corporations own them outright. So this seems suspicious I would say.
I mean I often see news about some CEO or other selling shares, and how this is announced in advance to not be insider trading. I have even seen sometimes the documents submitted to the SEC posted on the net. There are no trusts involved.
I'm not sure many financial advisors for the super rich would be recommending this method based on this.