Custom dynamic tag context

Following the docs here for creating a custom dynamic tag. I noticed in the post custom field dynamic tag, the tag uses get_post_custom_keys to get all post meta for the post being previewed in the template builder. So when you go to pick a custom key, you get a dropdown with all the post meta for the post being previewed.

However, if I do the same thing in my custom dynamic tag, I get the custom fields for the elementor template post being edited, not the post being previewed within the template builder.

I couldn’t figure out how the post custom field dynamic tag is setting up the postdata to ensure it gets the correct keys from the get_post_custom_keys call. Any chance you can shed some light on that?