There's a big difference between correcting some random commenter on an internet forum and correcting Microsoft.

> think it’s counterproductive. Most people only see a squabble, which makes any ensuing points from the open-source community seem silly.

Only to people that truly don't care whether something's open source. In which case, Microsoft using the term (correctly or incorrectly) won't change their perception.

But the people who do care won't like to be mislead by Microsoft. There's a reason the term is right in the headline: people respond to it.

I wish I had time to come up with a better example, but it's like if a AAA game company says they've released "native Linux build," but really they're just packaging the Windows build with Wine.

99% of people won't care, neither about the news nor the deception. But for that last 1%, any goodwill garnered with the headline would be gone, and the game company are the ones who look foolish, not the people calling them out.