The API is working as intended.
The examples you gave are not retweets of the original Tweet but actually only quotes of the original Tweet. Even though the Website calls those Retweet with Comment, it’s not really a retweet. As far as I know there is no API to get all tweets or users that quoted a specific Tweet, sorry.
(Maybe @andypiper has a bit more information about that?)
(A tweet is considered a quoted Tweet if you Tweet something that contains the URL to another Tweet as the last thing in this Tweet, the Apps and Website display those as inline “quotes” and the API additionally exposes some information about that quoted tweet in the tweet object)
