> but you could implement it on top of native widgets if you wanted to

Is there an immediate mode GUI API that uses native widgets? I don't think I've ever seen that but would be curious to try it out. Does it work well in practice? If it doesn't exist, then it's kind of a moot point, isn't it?

I sympathize with wanting "consistent behavior across multiple platforms", but that usually just results in "consistently kneecapped behavior across multiple platforms".