At a curosry glance, this doesn’t embed content from Twitch.
Content/highlights are served by them from their own system. And that highlght/video is exported from Twitch to their service.
So whilst they embed streamers content from Twitch in a banner, they don’t get that content from Twitch but their own server. So the streamer provided the video to that site to that site to use directly.
*Not a lawyer and only my opinion.
Either way if you think it’s violating the rules, legal@twitch.tv is probably worth an email