I didn't have full blown apnea diagnosed, but I did have very bad snoring and mouth breathing, resulting in poor sleep and issues functioning during the day (I even got into two car accidents due to microsleep). I feel like it's good advice, since my life has been transformed by working on my tongue posture. Unfortunately I didn't learn about it earlier, since I was mouth breathing in childhood and have a very small recessed jaw because of it. The base of my tongue would just always fall behind and close my throat, my head posture was always forward.