Hello,
This is the expected behavior, although it is different than kill dry on our stompboxes which fully removes the dry signal and only gives a wet output with a level control.
Kill Dry on Blackhole immersive will completely mute the audio input, allowing you to hear how the tails ring out and fine tune the size/feedback/gravity etc.
Kill Wet will only mute the wet signal (the dry signal will pass through), which is more useful when you have long reverb tails and you’d like to quickly mute them.
If you set the mix to 100% it will be effectively the same as how kill dry works on our stompboxes. You can adjust the wet level by using your DAW’s channel faders.