Recently, it was discovered that Apple updated the platform security documents, and found that the iPad Pro 2020 "hidden" function, then use hardware-level technology to disconnect the microphone connection to prevent eavesdropping. Specifically, when the user closes the protective cover, the iPad Pro 2020 will disconnect the microphone connection, not at the software level, but at the hardware level.
In fact, such a function has been realized in the T2 chip in the MacBook Pro in 2018, but it has not been added to the iPad for a long time. It was not officially introduced until this year's iPad Pro 2020. However, users must have an iPad Pro 2020 protective case approved by MFI to use this feature.