vue3.2.47 registering components Issues

[echo9z]

The following App builds the App component using the option api, while the self-packaged count-to-v3 component is built using <script setup >

    <div id="app">
      <CountTo :startVal="0" :endVal="2000" />
    </div>  

    <script src="https://unpkg.com/vue@latest"></script>
    <script src="/Users/echo/v3-count-to/dist/count-to-v3.iife.js"></script>
    <script>
      const { ref, computed } = Vue
      const App = {
        name: 'App',
        setup() {
          const str = ref(5)
          return {
            str
          }
        }
      }
      const app = Vue.createApp(App)

      app.use(CountTo)
      app.mount('#app')
    </script>

app.use(CountTo) register component times warnings

[Vue warn]: Failed to resolve component: countto
If this is a native custom element, make sure to exclude it from component resolution via compilerOptions.isCustomElement.
at

[echo9z]

this registers setup script so that custom components can be used normally

    <div id="app">
      <CountTo :startVal="0" :endVal="2000" />
    </div>  

    <script src="https://unpkg.com/vue@latest"></script>
    <script src="/Users/echo/v3-count-to/dist/count-to-v3.iife.js"></script>
    <script>
      const { ref, computed } = Vue

      const app = Vue.createApp(CountTo)

      // app.use(CountTo)
      app.mount('#app')
    </script>