Myth: agile = Scrum?!

I don’t stop wondering how many articles about „agile” methodologies use scrum terms like sprint out of box without any clarification, like if the only way to implement agile would be to follow scrum methodology. I have nothing against it because my company is also applying exactly Scrum methodology as par of our „agile movement”, I’m just wondering for reasons why people are promoting the myth with their articles...

For example Robert Walsh and Megan Sumrell discuss (in otherwise great article that I recommend and will refer in future) testing issues as development converts to agile. They talk about Sprints, even Hardening Sprints and other Scrum methodology elements.