Ah, so we talking about two different things here:
a) with any given UI design, distinguishing if it's implemented using native UI framework or with Flutter
b) Flutter app providing 100% indentical look&feel to Cupertino/MaterialDesign/WinForms/Cocoa/etc.
I was talking about a). Assuming that the app developer wants to have a consistent app design across platforms, which probably came from a design department – there is virtually no way to distinguish. Ultimately, it's just a bunch of pixels spit out onto the framebuffer.
a) with any given UI design, distinguishing if it's implemented using native UI framework or with Flutter
b) Flutter app providing 100% indentical look&feel to Cupertino/MaterialDesign/WinForms/Cocoa/etc.
I was talking about a). Assuming that the app developer wants to have a consistent app design across platforms, which probably came from a design department – there is virtually no way to distinguish. Ultimately, it's just a bunch of pixels spit out onto the framebuffer.