I’m a little surprised that you are complaining about a lack of context. Your first example is a direct quote from an early user of Flutter and I provide the link to their article, which has plenty of context.

Your second example — about control over the smoothness of their app — is one of the main points of this article. Dart allows us to lift the widgets, layout, gestures, even the renderer, and more into the developer’s app, so they have total control over them.

This allows developers to modify and optimize almost anything in their app, which is something you can’t do when you are using the OEM widgets, layout, and renderer from the platform. Even worse the OEM widgets often change with each platform release, making it difficult to optimize for all targets.

Flutter avoids this problem by using the same widgets for every OS version. Flutter also provides tools to help you optimize the performance of your app.

So to answer your question “What does far better mean”, when you go from having no control over the widgets or layout, to having full control, I think that counts as “giving the developer more control over the smoothness of their app”.

I’m sorry you missed that context.