why deep property change will trigger a shallowReactive object`s denpendencies?

[lijingfaatcumt]

Version

3.0.4

Reproduction link

https://jsfiddle.net/rxpcL210/1/

Steps to reproduce

const origin = { a: {b: 2}};
const reactiveProxy = reactive(origin);
const shallowProxy = shallowReactive(origin);
watchEffect(() => {
console.log('shallow', shallowProxy.a.b)
})
watchEffect(() => {
console.log('reactive', reactiveProxy.a.b)
})
window.s = shallowProxy
s.a.b

What is expected?

s.a.b change do not trigger dependencies

What is actually happening?

s.a.b change trigger dependencies

[LinusBorg]

tracked in #2843