T-Mobile is no longer touting the clear blue skies before a nationwide 5G rollout as the main argument for its merger with Sprint, according to Bloomberg's FCC sources. If you remember, that was the chief advantage put forward when the merger was co-announced by the T-Mobile and Sprint CEOs in the video you see above.
The Un-carrier knew that the 5G rollout is a priority for the administration, and decided to get on its good side, but the idea is no longer flying with the FCC, it seems. What T-Mobile did in its latest November filing, is arguing that the merger will put the resulting carrier on an equal footing with the Verizon and AT&T juggernauts, compared to fighting them now alone in the dark.
The reasoning might be the core competencies of the agencies who have the actual final say in the merger approval. While the FCC is looking for ways to enhance the public interest in any such deal, the Department of Justice needs to see that it will keep competition alive and healthy in the field.