Probably in response to City fans singing "You cheating bastards, you know what you are" at their ground last season. I wouldn't take it too seriously to be honest.
I thought the atmosphere was pretty good for most of the game last night, despite the no shows. Difficult to gauge it for sure when underneath the overhang of SS1 Block 115(!) as it's normally loud in that part of the ground but I noticed there were plenty of chants starting from elsewhere that spread. Couldn't really hear the Forest fans too much but again, it's not the best place for hearing the away fans where I was. Maybe they were louder than I thought?