Great question. idk about Sharrock but:
Individuals with hyperthymesia can recall extensive details of their own lives, along with public events that hold personal significance.[7] They often describe their memories as uncontrollable associations: when presented with a date, they immediately "see" a vivid depiction of that day without conscious effort.[8] These memories are strikingly detailed but not literal recordings of experience. In the case of Jill Price, anonymised as "AJ" in the 2006 study by Parker, Cahill and McGaugh,[1] her recollections resembled a movie running in her mind, yet she could not remember incidental details such as what her interviewers were wearing hours earlier.