USB-C to Headphone Jack with iPad Pro 2021: no microphone

Hello,

two weeks ago I bought an iPad Pro 11” 2021 (with M1), yesterday I bought an original Apple USB-C to Headphone Jack, I would like to use my old Apple 6S headphone with FaceTime.

Everything is ok if I use the headphone for listening, but if I open FaceTime and try to call a friend iPad always choose to use the internal iPad microphone and not the microphone on the headphone.

Is this the expected behavior or I’m missing something?

Thank you!

sandro