Why single out WebViews? Would you consider Flutter native? It renders widgets on its own just like a WebView does.
It's pretty much impossible to embed properly without edge cases in GPU-based renderers as far as I know, if you want layering of widgets (for instance a platform widget in-between two flutter widgets in z-order)
You can also hook a WebView up directly to a low-level language and skip Javascript entirely, so does that mean Rust + WebView = Native?