There are 3 functions to that button, all described in the owners manual.
1) It will launch the infotainment google assistant with a press and release (assuming a connected phone is not ringing)
(2022 Yukon Onwers Manual, Pg 166 under "Infotainment Section")
2) It will answer a connected phone if ringing
3) Pressing and holding it for 3 seconds will launch a connected phone's voice assistant (Google Assistant when using a connected android phone and Siri when using a connected iPhone)
(2022 Yukon Owners Manual, Pg 168 under "Steering Wheel Controls")