What problem does this feature solve?

vue2, we can code like:

   this,$once(''hook:beforeDestory',  dosomething)  

but vue3, i can not find events like this,

What does the proposed API look like?

<children @hook:beforeDestory="dosomething">

use "@vnodeBeforeUnmount" instead

use "@vnodeBeforeUnmount" instead

Is there any reference document for this api?