Maybe you don't understand what disinformation is. It's not just about saying things that are factually untrue, because that's easily countered. More often it's about changing the interpretation or emphasis to promote a preferred narrative and/or create an illusion of popular support. Other times the goal is just to sow confusion or conflict.

For example, consider how "good guy with a gun" incidents are covered by the media. Some would say they're inappropriately suppressed in mainstream news. Others would say they're inappropriately celebrated in niche news or entertainment. I'm not here to say which is right, but both could be considered disinformation. They're trying to shift the narrative toward an ideological position, regardless of actual truth or proportionality.

So no, I don't agree that something must be untrue to be called disinformation. Presenting it that way is itself kind of treading the line.

There is a difference between an instance of an individual person sharing a true idea to convince others, and an organization which claims to report the news but selectively reports true news for propagandistic purposes.