Self-view in smartphone when host is sharing screen

Hello!

I always use Zoom on my computer, never on smartphones. Recently, while I was teaching, I started sharing screen. Immediately, my student, who was using a smartphone (an iPhone, I think), couldn't see himself anymore. He then asked me how he could see his self-view again while I was sharing my screen. Since I never use Zoom on my smartphone, I didn't know how to answer. Later, I tried to simulate the same issue using my smartphone and I also couldn't see myself while the host was sharing screen. So I came here just to confirm with more experienced users if it's really impossible to have self-view on smartphones while the host is sharing his/her screen. 

Thank you all for your help!