I won't get into whether or not it's fair to call call "developers" "engineers", but I do make the distinction in the first paragraph that the article refers to software engineers. In addition, velocity, bug count, and lines of code are all software terms. I can't imagine anyone thinking this is referring to any other type of engineering.
Agile, for example, is another general term that has a fairly specific meaning in this context.
If you overhear someone in a park say "Oh, you guys are agile? What's your average velocity?" would you assume they are talking about athletics or software development?