The problem of level issues encountered in the design of LattePanda_Mu carrier board

Hello
Recently, I was designing the carrier board for LattePanda_Mu. However, when referring to the official pull-out carrier board circuit diagram, I had some doubts. In the 232 design of SIO_UART, the 232 level conversion chip is powered by 5V. I'm not sure why this is the case. Shouldn't the level of SIO_UART be 3.3V? I don't quite understand this.