If you want to get technical, we should be using Mach number or knots since that’s what the world uses for aviation. That being said, the majority of the article’s consumers aren’t technical with this topic :P
Sure, if you also want to say water doesn't freeze at 0C or boil at 100C. In practice if an author casually leaves out the variables needed to calculate ground speed from mach or airspeed, it usually means they're doing engineering calculations set at the ISA standard day model (sea level, 15C, no humidity).
I replied above, but knots have a similar problem when flying (indicated air speed).
If you ask a pilot, ground speed only really is important for calculating ETA. Everything relevant to flying is a relative number since atmospheric density is fluid.