Apparently it was video clips originally posted, but it seems like posting unpublished(?) copy of any type can fall under DMCA, which I guess makes sense.
-> [HBO Lawyer] classifies the infringing content as 'summaries of unpublished, character, setting, and plots of a forthcoming series'
-> [HBO Lawyer] classifies the infringing content as 'summaries of unpublished, character, setting, and plots of a forthcoming series'