Yes. It is for "JS Sprinkles" on your existing HTML. This makes it "modest" compared to something like React that would typically generate HTML/DOM for you.

To understand their philosophy, see DHH's blog post announcing Stimulus 1.0, https://m.signalvnoise.com/stimulus-1-0--a-modest-javascript...

The idea is you render the html as is. The data attributes take care of the interactive parts, with the js scripts loaded after the page renders (as opposed to render html within js that executes on load with, the reactjs render() call).