Doubts about using v-model when getters return objects

[ParkerFiend]

Reproduction
https://stackblitz.com/edit/github-i1nwig

When I use getters to return an object,
I also use input boxes to v-model bind the object's properties.

At this point, manipulating the attribute values in the input box will directly change the corresponding data in the store(input2).
But if I set getters directly for specific attribute values, this situation wouldn't happen (input1).

If I want to be specific about the attributes and achieve the effect of the second input box,
I still need to use both Writable Computed and storeToRefs(input3).

Does this meet expectations?

How do I understand and use the above situations in the project?