Classic grifter - 95% of his backstory is made up.
You can achieve far greater enlightenment by simply droping your preconceptions about rich and poor people and understanding the very basic day to day things happening around you than you will achieve listening to him.
However, the priority order on your OS for address selection, even when it comes to stuff like choosing which DNS results to use is IPv6 global address > IPv4 > ULAs. So on a dual stack network, ULAs with not be used unless the only address is a ULA.
And even if you run your internal services with only an AAAA record pointing to the ULA, the client's source address will likely be the global address of the client device unless you tweak the tables on each client, which then means you'll need to have your global address in all your firewall rules to access the internal services on ULAs, which then means you're not saved from having your ISP-provided global address in your configuration, which is what you were trying to avoid by using ULAs.
You can achieve far greater enlightenment by simply droping your preconceptions about rich and poor people and understanding the very basic day to day things happening around you than you will achieve listening to him.