I’m having trouble with this using the nightly builds from the Firmware builder. I selected the options for MPTC and to add the MPTC menu option for tuning.
On my Ender 3 Pro with v4.2.7, Sprite Pro and a BLTouch, I get no activity in response to a M306 T - it just returns the current values. There’s also no menu option for tuning on the LCD screen.