It isn’t native in this context; As a sibling comment mentioned, OniVim2 uses revery[0], which uses it’s own widgets (not native ones) like flutter[1].
Quoting from my old comment[2]:
> We really should be trying to use the native GUI toolkit (or cross-platform native UI libraries like libui), not using Flutter-esque libraries that draws everything from scratch.
> Coherent UI is a very important point to users IMO. Users can assume that some special feature from App X will also work on App Y.
[0] https://github.com/revery-ui/revery
[1] https://github.com/revery-ui/revery/blob/master/README.md#de...