Actually, the appbar is partially under the status bar. It just has an internal padding to handle it correctly
This is very clear when you remove the appbar :
Scaffold(
body: Text("Hello"),
)
In this situation, it will render “Hello” under the status bar.
You can fix this by wrapping your body into a SafeArea :
Scaffold(
body: SafeArea(
child: Text("Hello"),
),
),