Because science isn't about generating indisputable facts. If that's what you're doing, what you're doing isn't science. The epitome of good science is a predictive and well-supported theory like evolution.
Adding the word "just" implies a misunderstanding of how the scientific method works, because it doesn't get any better than a good theory.
If you read between the lines "not trying to own the ecosystem" is just business talk for "we want ya'll to feel safe about buying into the thing we've built, so at the end of the road when we own the ecosystem, the checks go out to us". There's nothing wrong with that, as long as you understand what they mean.
Remember that Docker is a funded business, that has an obligation to its investors.
Adding the word "just" implies a misunderstanding of how the scientific method works, because it doesn't get any better than a good theory.