could you point to that part of the article? I must have missed it.
When I was an undergraduate I thought I was smart enough to be a physics major. So I took a lot of physics classes. Trust me. When physicists talk about light they are talking about the entire electromagnetic spectrum. ‘Cause it’s easier to say, “The speed of light is c,” than it is to say, “the speed of all frequencies in the electromagnetic spectrum is c.”
Unfortunately, this causes a lot of confusion among laymen because they’ve always been correctly told that light is only a small sliver of the electromagnetic spectrum that your eyes can actually see. But physicists don’t have occasion to talk about that part of the spectrum very often. So to them light means the whole thing.