Nice article. I agree that owning every pixel is what makes Flutter stand apart from other cross platform frameworks.
I do worry about a narrative around Flutter that it caters to the whims of designers. It could create a strong association between Flutter and poor mobile app design. (Remember Android before material design?)
Mobile App design is tricky and many designers just don’t get it. They break well known navigation paradigms or mix iOS and Android UI elements, conceive “unique” interactions, often with no usability testing. This is then often justified with claims of creativity or pushing boundaries or standing out.
I would hate Flutter to get a reputation as the framework that doesn’t especially care about apps “fitting right in”.
I vote that the Flutter developer community uphold platform UI standards and encourage designers to use them rather than let the ability to own every be abused.