The first thing that comes to mind regarding GCTS is that the VOR is SW of the aerodrome.
It is possible to reduce the circling area (exclude a portion of the total area) in order the acheive lower minima. This has been done at GCTS.
However, when this is done the area in which obstacle clearance is provided has to include those parts of the final approach and missed approach that are in the total circling area.
With the VOR a distance from the runway, the final approach area and missed approach area will splay outward i.e. get bigger as one moves from the VOR towards the runway.
The ILS however, will have the area reducing in width as one gets closer to the runway.
Thus it is possible that the circling area in which obstacles have to be considdered is different for the VOR and the ILS.
However, for me the biggest clue could lie in the fact that the ILS charts refered to are some years older then the other approach charts.
Therefore, until I had the situation clarified, I would use the higher minima as published on the later charts.