We can't really know if they broke their implementation of the Signal protocol because it's not open source and the code cannot be reviewed by the public. Howev

We can't really know if they broke their implementation of the Signal protocol because it's not open source and the code cannot be reviewed by the public. However, they have openly explained how reporting messages exposes the contents of messages and why it doesn't break the E2EE. All we can do is trust their explanation. Or, don't. And don't use it. I don't.