You are correct that it isn't Open Source as defined by the Open Source Initiative, nor does it use an Open Source Initiative Approved License.
None of that information, however, is helpful to the author or really changes anything about the article.
If an important distinction like this is fading from our language, it's probably evidence that newer members of the community haven't been fully educated on the implications of software licensing terms, and if that's the case we should focus on improving that education, not resign ourselves to important knowledge being lost by the community.
For instance, if you learned that young people were not aware of the dangers of exposure to lead, you would not throw up your hands and say: "I guess we'll just start using lead pipes again". You would make an effort to pass on that knowledge.
I agree with your position. Open Source is not a meaninglessly unclear term, it is a precise term of art. It makes good sense to resist efforts to turn it into a meaningless marketing term like premium.
Some people point out that the term isn't trademarked. That doesn't matter. That isn't how terms of art work.
As in, "hey come to the seminar with me on Thursday: there's pizza and free beer."
Even as a non-latin speaking person I can identify the difference between those types of "free".
Or, alternatively "Free as in Freedom", which is another phrase I've heard coming from the FSF.
Free as in beer is used in contrast with Free as in freedom, and refers to something made available free of charge.