Understanding onTrigger

[diwic]

The following playground script:

<script setup>
import { unref, computed, watchEffect, reactive, ref } from 'vue';

const count = ref(0);
const data = reactive({});

data.timeout = computed(() => unref(count) > 1);

watchEffect(() => {
  if (data.timeout)
    console.log("Timeout!");
  else
    console.log("No timeout!");
}, {
  onTrack(e) {console.log("Track", e);}, 
  onTrigger(e) { console.log("Trigger", e);}}
);

</script>

<template>
  <h1>{{ count }} {{ data }}</h1>
  <button @click="count++">Click</button>
</template>

On first click on the button, there is one call to "onTrigger" (expected 0 since "data.timeout" does not change). The watcher is not run.

On second click on the button, there are one call to "onTrigger", two calls to "onTrack", and the watcher is run.

I'm currently debugging a more advanced scenario. Is there a way to understand why or why not "onTrigger", leads to the watcher being run or not?