I've noticed that changing the Stereo Interleave button to Mono from the track itself does not force an inserted Mono plugin to stay Mono (FX bin still shows two pins), only using the Interleave button from the Mix Console itself changes the pins from stereo to mono and vice versa. Otherwise, inserting a Mono plugin with the Interleave set to the default Stereo forces the Mono plugin to Stereo (two pins). I am using UAD plugins to test this, as I need to use the Mono versions of these plugins to get reduced DSP usage that the Mono versions afford. I do recall this behavior changed about the time that the Stereo/Mono Interleave was taken out of the audio track controls back before SONAR Platinum. They were later put back in but have never really worked right, as when using from the Mix Console itself. I have just got in the habit of using the Interleave button on the Mix Console itself when changing the Interleave status.