This isn't really a thing -- it's a theory that rarely happens in practice. It can happen. Larry Ellison has taken billions in loans backed by Oracle stock to pay for yachts and things. But this hides a lot of things. For example, beyond just a few million dollars, his estate already pays 40% tax
For the fabulously wealthy, paying taxes is pretty much optional. They can borrow against their vast wealth, which is mostly an untaxed capital gain, without paying taxes. When they die, the capital gain goes to zero. And loopholes exist to bypass the estate tax too.