I think you are just misreading the article. Nobody said anything about big antennas on submarines transmitting. The only new information contined is from a speech by the head of submarine operations saying that submarines are important to signals intelligence with very little detail. (Yes this is PR for submarines.) The rest is old news and somewhat confused speculation.

In reality this non-story appears to simply be something convenient for the WP to tack on 2 paragraphs of Trump attacks. Kinda weird.