defineModel behaviour is not the same as prop + event syntaxe anymore

[ChamNouki]

Hello dear fellows 👋

I'm confronted to an inconsistent behaviour between defineModel and it's older and fully qualified syntaxe using a prop and an event.

1. Using defineModel
   When I assign the same value to the model as the model actual value, this doesn't emit event to the parent component. This behaviour comes from defineModel is triggering update event, even if its value didn't actually change #11125 and associated merged PR.
   defineModel use case

2. Using prop and event
   On the contrary, emitting an event with the same value as the previous emitted event trigger the update on the parent component.
   prop+event use case

This behavioral difference is quite annoying in my opinion : the library should not take the responsability of choosing when to emit or not the event when assigning a value to the model through defineModel. Especially when the documentation says that defineModel is only syntax suggar for the prop+event syntaxe to be able to use v-model.