I think the energy-saving production is the real benefit, like you said.
According to calculations by Zhang and his colleagues, the new technology could improve the energy use efficiency of China’s steel industry by more than one-third. As it eliminates the need for coal entirely, it would also enable the steel industry to achieve the coveted goal of “near-zero carbon dioxide emissions”, Zhang’s team added.
Obviously it remains to be seen if this pans out. "Could" and "does" are different things, after all. I could just as well imagine every efficiency gain being wiped out by the Jevons effect.
It's a continuous process, think of a conveyor belt. If the conveyor belt is 3 feet long or 3 miles long, the rate you can put things on it is the same.
Yes, that has nothing to do with the time the items have to sit on the conveyerbelt. This is a process that takes 3600x less time, not one with 3600x more throughput.
If they put 1 ton of iron ore in the furnace over a period of 1 hour, even if the iron is at the bottom of the furnace within seconds instead of hours, it doesn't enable them to add iron ore at a faster rate.
Your made up scenario has absolutely nothing to do with how the process actually works though. You literally just made a straw man here. The reality is that the iron has to sit in the furnace for less time, and that means you can put more iron through the furnace of a particular size than you could otherwise. This really shouldn't be a hard concept to grasp, yet here we are.
If they put 1 ton of iron ore in the furnace over a period of 1 hour, even if the iron is at the bottom of the furnace within seconds instead of hours, it doesn't enable them to add iron ore at a faster rate
Cool. So, now they get to put several times more of the iron. I wonder if your argument is going to be 'but they will hit another bottleneck, then'.