I rather think we're drifting off into la la land here....
There's surely a world of difference in the police getting involved in a domestic situation on home territory where the police can swiftly carry out background checks on the occupants etc and neighbours/local community might well know something about the occupants too. At OC the occupants are almost exclusively holiday makers renting apartments for very short periods of time where the authorities would have no idea about the occupants without referring to OC nor would the other residents/holiday makers have any idea either. PF was in a unique position in that she was the only full-time resident but even so she only had knowledge of the McCanns over the 3 days prior to the crying incident. I can't see any reason whatsoever why she would be expected to take it upon herself to get involved and go investigate the crying.
At the time she heard the crying she knew nothing about the family. They hadn't disturbed her before that because they were out most of the time. All she knew of them was having seen them walking around the resort.
Her friend Edna Glyn's reaction shows, perhaps, the attitude of local residents to the holidaymakers. She 'wasn't surprised' when told that a child had been crying for over half an hour. Perhaps it wasn't unusual in a resort where adults were given free booze with their dinners that they were slow to respond to a crying child.
Mrs Fenn didn't say that she knew the children were home alone on 1st.