Hmmm, interesting. I never thought about breathing being an issue, however I don’t hold my breath (that I’m aware of). I’m one of those people whose cheeks puff out as I breathe out, so I know there is a decent airflow there. However, I do use a nose plug (always have) since I have issues with sinus infections and as a fairly newer swimmer in the past couple years am not so great keeping water out of my nose.
Think that is limiting the air flow enough? I know I can swim without one, I’m just more comfortable with it so I’ve always used it. However I’m willing to ditch it if you think it would help!