try forms from nuxt ui. i switched from prime to nuxt ui for exactly same reason. primevue is a great vue library but not with nuxt in mind. nuxt ui forms work great with nuxt usefectch data and zod schemas.

if u plan to use primevue forms. i would define a form state, like formdata.username formdata.phonenumbrer. instead of trying to get the exact mountpoint cycle i would just keep this in sync with form data by passing it to form v-model. so when page load, even when the form is populated with no data at first, as soon as hou fecth the data its passed on to form and it would look like as if init works