Many dj mixers offer the option to split the main mix to one ear and the cue’d track to the other, i have never been able to mix like that, only with cue on headphones and main mix out in the room/monitors. Weird

Everyone can be different and that's ok.

I know dj's who can rarely hear the song that's currently playing, and only hear all the other songs that can play with it.

Experiencing music is the gift :)