Anyone can start an organisation and define "open source" the way they want.
The common way it is understood should probably be named "libre source" or something, because it means more than that the source is just out in the open.
Sure anyone can, but OSI is the organization that popularized the term in the first place and its definition is widely followed, so there's no need to make such point in this particular case.
That’s not how human languages work at all. A term picks up common or agreed use. When you try to push against that, you see the exact reaction you’re observing here.
