Thank you for the tutorial! However, I am not able to replicate that. I even contacted tech support and they were unable to replicate it either and have forwarded it to the developers. Clearly you are able to, but on export, mine reverts to 16:9. I have attached my process and the email from tech.

That is where after the edits have been made (choosing which camera) you can set one of the original tracks to be the master audio track (I recommend the track that starts the multi-cam track itself). This will replace the audio in edited track with the original - thus no breaks.