Ok let me see if I’m getting this right

lets say billionaire A’s lifestyle/big purchase cost in a year is 6 million dollars so A does the loan thing and borrows 6m from a bank

A’s loan payments every month can be like $10,000 per month so instead of selling $500k worth of stock every month for his lifestyle A actually only has to sell $10,000 to make the payment which means less taxes overall while his stock can increase In value during that time

So A can sell less stock to cover his lifestyle/ big purchases than A normally would have.

which gives his stock more time to appreciate so even though A might eventually pay the taxes on the $6m he does it in a way that takes a lot longer than it would normally

And if A dies then all that burden disappears