The child component by default inherit the declared attributes. Vue3 calls it the Fallthrough Attributes.
A "fallthrough attribute" is an attribute or v-on event listener that is passed to a component, but is not explicitly declared in the receiving component's props or emits. Common examples of this include class, style, and id attributes.
If you do not want a component to automatically inherit attributes, you can set inheritAttrs: false in the component's options. These fallthrough attributes can be accessed directly in template expressions as $attrs.