Carport using unusual construction method

Okay. Keep in mind that cement and concrete are not the same thing. Cement is a component of concrete. Concrete consists of rock, sand and cement which is actually a glue or a bonding agent, used to hold it all together. The rebar acts as a skeleton to bind the concrete together to resist tension. Concrete in itself is excellent at resisting compression. This is why it is an excellent material for driveways, columns and walls. It is the imbedded reinforcing bar that gives concrete the ability to resist deflection in overpasses and bridges.
I see that you mention a concrete filled steel pole. Obviously the job has been done now and all that you can do is hope that it holds together. My thought though is that part of what makes rebar better idea is that the irregular surfaces of the rebar make a better "grip"for the concrete to grab. A smooth pole sorta reminds me of a fence post in concrete. Sometimes when one is pulled out of the ground, they slip right out of the hole, sometimes the whole chunk of concrete comes with it.
I am not trying to piss in the punch bowl here. Sometimes unusual stuff works out quite well and becomes the new way to do things.