"Steam" is only produced by the boiling of liquid water and it is over 100°C. Steam is going to scald and it's going to hurt. No one puts actual 100°C steam up their nose. That article makes no sense to suggest people regularly do. The people cited with burns seem to have accidentally tipped boiling water on themselves.
What people generally call "steam" in regards to "steam inhalation" is actually an excess of condensed water. An excess of condensed water is what you see in the bathroom when you take a hot shower. Most clouds are condensed water (sometimes they can be ice crystals.) It isn't technically "Steam" at all, and it isn't hot enough to burn.
When I've used a eucalyptus or other plant oil steam inhalation myself, it is the plant oil vapour that acts on the mucus membranes rather than the condensed water. The very hot water just vapourises the oils.
