Question about content_attributes prop in radix:page-content component

I've been spending some time learning about Radix and how things are put together.

Looking at the radix:page-content component, there is a content_attributes prop that is not required, nor is it initialized in the page-content.twig file - this leads me to believe that it is expected to always be passed in to the component. Otherwise, I'd expect to see something like this:

{% set content_attributes = content_attributes ?: create_attribute() %}

Looking at the radix:page component (which includes the radix:page-content component), no value of content_attributes is set. Same goes for page.html.twig (which calls radix:page).

I searched the .theme files and didn't see any mention of it anywhere.

In the radix:page-content component, it is used as follows:

<main{{content_attributes.addClass(page_main_classes)}}>

This leads me to believe that it should be initialized at the top of page-content.twig with

{% set content_attributes = content_attributes ?: create_attribute() %}

Or, am I missing something?

thanks,
-mike