Child component with props only updating if the prop is used in the child's template

[fxdave]

Version

2.5.21

Reproduction link

https://jsfiddle.net/te8kcj1u/

Steps to reproduce

Do not use props in child template, and try to catch the updated property in the child's updated hook.

What is expected?

It should catch the prop

What is actually happening?

It is not catching the prop

[posva]

if you want to watch a prop being modified use $watch. the updated hook is when the component vdom changes (as stated in the docs)