Should EditorView.baseTheme always be applied?

I was slightly surprised to find that a theme defined using an EditorView.baseTheme extension (as opposed to EditorView.theme) is applied even to editors where the extension isn’t active.

After some reflection (and this comment) I think this is probably intentional, but maybe someone could confirm that this is the intended behaviour?

Yes, this is intentional. This is how you define the base styles for the DOM stuff that your extension adds. Use theme for actual conditional theming.