I wonder if this works only for games, as the above examples. I am trying this with school software, and have added a YouTube URL, formatted as specified, about 4 weeks ago. The video is still not auto-playing.

I read somewhere else that supposedly, reasons could be

• The promo video is not in a supported format.
• The promo video is longer than 30 seconds.
• The promo video has a file size that is larger than 50 MB.
• The promo video has an aspect ratio that is not in the range of 9:16 to 16:9.
• The promo video is too short.

No idea if this is true, it's not mentioned in the google play console docs (which are not very detailed).