This is true, but they are capable of housing "millions" in the same way that I am over 1 inch tall!

Each ring would have tens of thousands of times the surface area of the Earth, and could easily house trillions if not a quadrillion people.

If this were possible, of course. It turns out that a ringworld like this isn't stable, so each ring would have to have huge thrusters which were constantly operating to prevent the ring from falling into the sun. And there's the question of what material they could be made from, given that no known material has both the strength and the stiffness needed...