It's an actual process. The ability of hydrogen to reduce hot iron oxides to metallic iron has been known at least since the early 19th century. But it has not been done on an industrial scale before because using fossil fuels is cheaper, and reducing GHG emissions has not been a significant priority until recently.

EDIT: Joseph Priestley actually discovered that iron oxide ("calx of iron") could be reduced to the metallic state by hot hydrogen ("inflammable air") in the late 18th century.

https://archive.org/details/b22281824/page/n57