Sure, we can't know that about every conversation. However, everything we do know about Harry's most recent meeting with the Queen has come from the interview he himself chose to give about it to an American TV network. And in that he chose to claim that she speaks to him about certain things and no one else 🙄and that he thinks she is bored of birthdays! So the recent evidence suggests he is currently perfectly willing to trade on his relationship with the queen, and compromise her privacy, for his own interests. The signs aren't good.
The latest Private Eye, btw, says that communication between the Queen, Charles and the Sussexes has been virtually zero for a while. I am far more convinced of the credibility of their inside info than of PR stories about Zoom calls.