https://wccftech.com/new-ipad-pro-disables-the-microphone-on-a-hardware-level-to-prevent-eavesdropping-or-spying/

A feature which was exclusive to the MacBook has made its way to the iPad Pro lineup - close the magnetic case and the microphone disconnects on a hardware level.

Apple introduced a feature with the 2018 MacBook lineup, allowing the microphone to be disabled whenever the display lid was closed. This measure was put in place to prevent eavesdropping, preventing malicious apps to tap into the microphone to gather extra data about you.