I think you are right.
I deleted all 3rd party apps including Infuse, didn’t reduce disk usage much.
I enabled Aerial screensaver and weekly download new video, did a count, I have 90 Aerial videos downloaded in my ATV… each video can be up to 980MB so it explains why disk space was taken, somehow in previous tvOS this disk usage isn’t reported…
Although someone said ATV only keeps 3-5GB Aerial videos at any time (https://discussions.apple.com/thread/250889239), apparently it is not true.
But I couldn’t find a way to delete those downloaded videos.
So I did a factory reset and installed back all apps, rebuild Infuse metadata cache completely (browse thru every movie title to get metadata), Infuse metadata cache remains 1.5GB, ATV disk usage is now only less than 7GB. I am happy with that.
Btw, I noticed Infuse metadata fetching has been improved a lot, very fast and accurate, I used to take 6 hours to rebuild my movie collection, but it took me less than an hour this time.