This is the big problem with trying to tax the wealthy in America: There are just way too many ways to "not technically own" something, but still in reality be in complete control of it and benefit from it. Trusts, corporations, foundations: All these phony paper entities that you can "move" your stuff into in order to pretend to the government that it's not yours anymore, when it is in all reality totally controlled by you.
I worked for a founder once where basically everything he owned and benefitted from was owned by a "charitable foundation" or something. His homes, cars, boats, everything. He probably paid zero in taxes, whereas I, a chump, paid the normal rate. Total scam, but hey, that's what you get when the wealthy write the law.