Hydrogen isn’t burned in fuel cells, though? So hydrogen used in fuel cell, such as hydrogen powered vehicles, is indeed clean.

Sure - but I wasn’t claiming that consuming it always produced huge amounts of NOx - I was pointing out that having hydrogen involved doesn’t make a process “clean”. And burning hydrogen in air is being pushed/proposed - not just domestically in the form of hydrogen enriched NG but also for grid scale electricity generation in gas turbines.