The Chief Rabbi Allows the Use of Phones during the Sabbat

Rabbi Yosef also ruled that anyone who has been tested for coronavirus and is awaiting the results should leave his cell phone switched on during Shabbat, and should answer it with a shinui [in a different manner from during the rest of the week] in order to be updated on his status, in case he needs to go into quarantine. 

The logic of his ruling is clear, but once we start giving allowances to special cases, what remains? Anyway, he is not my rabbi. I am a Hungarian Jew.