The online iD editor is powerful enough for even pretty complex/big edits in my experience, with good basemap options and intuitive controls. I don’t see any need to download JOSM.
Exactly my thoughts. Advising to download and use JOSM to a novice OSM mapper to make their first edit there (to add a single tag, of all things) instead of iD is nonsense to me, just totally unnecessary overkill. I don’t even understand how article author decided it’s a good idea, to be honest.