I’m not sure if Twitch gets the game publisher to agree to certain image usage terms when submitting box art or not. You may need to check this.
Are you sure this is referring to the box art? Do you have any other images that it could be picking up on? Are you saving the images locally to the APK, or are you fetching them dynamically via the Twitch API?
I would imagine because they did not approve it the first time, this second time was a manual check by Google.
To be honest, right now, the best thing you can do is contact Twitch legal team and ask them about how you can use the box covers when fetching them via API. Make sure to give them as much detail as possible as they wont give you an answer unless they know all the facts. Then for the time being, if you really want your app published, just comply with Google and blank out the game covers and use text instead.
It’s a bit of a grey area between fair-use and copyright infringement, my guess is Google have started being cautious to new apps on the store. If there are older apps which use the same type of images, Google may be letting it pass because there has been no complaints for a year or so.