I don't believe that's true. (I didn't watch any of the speeches this year, but in past years it's been mentioned many times.)
Regardless if it does happen, are you trying to say a speech about mivtzah Tefillin would be banned the same as a speech about the importance of focusing on moshiach without being afraid would be?
The purpose of the banquet is to energize and pump up the Shluchim. The purpose of the preceeding days is to discuss the what, how and why.
They don't get into policy specifics at the political national conventions, though they will touch on broad concepts.
Sure, they mention tefillin. But they mention Moshiach much more than tefillin at the banquet.
A talk on mivtzah tefillin wouldn't "be banned", it would just wouldn't take place at the banquet. It happens at the sessions. There are many sessions about Moshiach, and many Shluchim have the very same concerns mentioned in the speech.