I'll adopt whatever definition you want "native" to mean for the discussion - and under your definition of native, I would say it's pretty clear that users of text editors and developer tools don't care much at all about "native"(your definition of using the platform provided widgets). Just look at the market share of developer tools and IDEs/editors that don't use stock platform widgets. They are the ones that have become dominant. The problems that people have with the dominant players that have gained traction is the performance. You might be able to make the case that using stock widgets matters for non-developer tools (and I would only partially agree there), but for developer tools when people say they want "native" they are more likely to mean they want the performance that more often comes with natively compiled languages without a VM. It makes sense that developers would trade stock platform-widgets in exchange for an editor with greater cross platform reach because users of these tools benefit from network effects of these tools having wider reach. They want someone to have written the plugin/extension they're looking for.

Personally, I'm not looking to increase the ways that I'm locked into my current operating system, so all else equal, I'd favor an editor that runs everywhere.

The other thing to consider is that developers spend up to ten hours a day in these editors. The biggest benefits of OS-coherent UI is that an application is quickly learnable for the first week. But when you use an editor for multiple years, all day long, many would trade that for increased customizability.

It uses the authors' own Revery [0] framework, based on ReasonML and GLFW. So there's Javascript in the stack, but no Chromium.

[0] https://github.com/revery-ui/revery