when ultimecia possessed edea, ultimecia was in full control which would explian why they shared thoughts. squall and c.o's consciousness being projected into laguna, kiros and wards past bodies only meant they were aware of something weird and it also somehow made them stronger ( i think faeries is supposed to mean the strange feeling the 3 get that helps them through battles and thats something to do with squall and his teammates strength.) seems as ultimecia has full control where squall is just watching and sharing thoughts slightly id think ultimecia's control would have bigger effects.