That feature is not about HTML editing (which isn’t really a use case for ProseMirror), but about structured text editing in general. Unless your schema is extremely simple (no block leaf nodes at all), you’ll probably need this to support certain editing actions. Even Google Docs has a feature somewhat like it (click a list marker, for example).
I do suspect your users will be able to figure out what a selected node means—this isn’t some weird mode that they get stuck in, since cursor motion will still work, and continuing to type will replace the selected node in a rather observable way.
That being said, more configurability around mouse actions would be a good thing, but it’s not something that’s currently supported.