Turns out we were directly outputting post_content, which avoided processing the blocks properly.
We’re having this exact same problem, did you ever find a solution to this?
I’m also very interested in this functionality…
I managed to figure this out. Pasting the updated code for everyone else that has this question.
The key was in calling the variables, you have to call it specifically from that post’s data.
$attachment_id = get_field('page_header_image',$p->ID);