See my reply to another forum thread Plex Guide HD channels missing when HD channels only selected
The way it works at the moment is that we filter on what is showing in the period - so channels streaming at 720 would get included even if SD channels and channels only streaming 480 in the period covered would be excluded if only streaming 480
It is being discussed with development as to whether it should be changed but some countries do not have the HD/SD channel identification and also it would result in loss of visibility of some HD content
