Black pipe and copper are the only two things acceptable for any application where is movement or vibration. Even the flexible hose behind your Sticks & Bricks gas stove is only good for one use. Where I live, it is against state law for an appliance dealer to replace a gas stove and not replace the flex hose also.
Copper is not the cheapest material to run gas lines, but the RV builders use it so that should be an indicator. They use nothing but black pipe and copper tubing.
Many owners come on here to ask for advice and when they don't get the answer they like, do it their way anyway, and that applies to propane, electrical, and anything else that can cause injury if not done properly, wire that happens to be on hand, air compressor quick connects for gas, etc. I hope it works well for all of them.