We are creating the tweets as another user using the “as_user_id” param of the tweets endpoint. Since the “POST statuses/destroy” designated for tweets deletion states you could use it only if authenticated as the author, how could you delete tweets you created on someone else’s behalf?
As you’ve discovered, the Ads API does not support deleting another user’s Tweets. However, your platform could obtain the ad account user’s tokens and call the destroy endpoint you’ve mentioned above - more in Accessing Ads accounts.