ScrollItem doesn't set classes

[foundryspatial-duncan]

With markup like this:

<scroll-item id="section-8" @change="itemScrolled">
    <p id="section-8" class="content-item">Deserunt architecto modi possimus ...</p>
</scroll-item>

<scroll-item id="section-9" @change="itemScrolled">
    <p id="section-9" class="content-item">Facilis culpa possimus natus eveniet,... </p>
</scroll-item>

The actual DOM of the app just has the p elements, and I expect their classes to change depending on the scroll position/state, but the classes never seen to change. I'm using Vue 2.6.6 with a custom scroll container.