What is the normal sense of the word? I only know the CIE standard observer to define colour and with this it is clearly in the equivalence class of orange.
I think they mean they don't emit a "natural" orange (like an orange flower) that is really some kind of sum of many wavelengths. I could be wrong though.
A pure orange contains only light with a single wavelength.
A mixture of light with different wavelengths that is perceived as orange cannot be distinguished from a mixture of some pure orange with a certain amount of white light.
So any orange, of a flower or of anything else, has the hue of a single wavelength, but it may be more or less saturated, appearing like light with a single wavelength mixed with some white light.
Low-pressure sodium lamps emit a pure color that belongs to the yellow-orange range, so you could describe it as a yellowish orange.
High-pressure sodium lamps have a desaturated orange color, i.e. light that looks like a mixture of orange and white lights.
The orange of any kind of sodium lamp is much more yellowish than the reddish orange of neon lamps with cathodic light, like those used in neon indicators.
Most sodium lamps contain some neon for starting, so when they are switched on they may emit a reddish orange light for a short time, then change to a yellowish orange light, when the sodium vapor takes over from neon.
