True - meditation means different things to different people. It's obvious the author is referring to the "mindfulness" version though and is trying to do so in simple-as-possible guide form so as not to distract with all the depth and nuance you allude to. I think most people get that there are many different types of meditation. I appreciate the article's simplicity because when I was a once a beginner all I seemed to be able to find was less than simple school-specific (Zen, Shambala, etc) instruction. The problem with the school-specific teachings, IMHO, is that they are all mindfullness-oriented, yet each adds their own special ritual and ceremony which as a beginner you mistake as being essential. At least for me, I've converged on an intentionally Occam's razor style approach aimed at stripping the non-essential. The coolest thing about Bhudda's story to me is he just sort of figured it all out for himself and said each of us should do the same. I've figured out for myself, for example, that it is not necessary at all to sit cross-legged. It makes no difference for me yet standard teachings always strongly encourage it to the point that you feel like you are "doing it wrong" if you don't. Teachers will even say, "if you can't sit cross-legged it's ok..." but when everybody in the group is doing otherwise, the overwhelming signal is it is actually not ok.
I guess one thing I'm saying is the kind of folks drawn to try meditation are often the same kind of folks who will willingly dive down rabbit holes investigating the differences between the schools and entertaining themselves with koans, etc. all the while distracting themselves from actually getting started with the meditation itself. Can confirm; was one of these people. That's why I'd caution against trying to raise awareness of all this complexity to the beginners this guide is intended for.