Did you not notice that little blue sign below the main sign ? That's why you got a PCN whilst the others didn't.
However councils seem to think that just putting up signs up like this one, mean they can ban parking beyond the sign, but it's more complicated than that. Parking off-carriageway has been an offence in London since the 70s, and requires no signs or lines. Councils can, however, by council resolution, decide to allow such parking on named streets. The problem is when they erect signs like the one here, it implies only part of the street is permitted for off-carriageway parking but they fail to put this into the resolution, so appeals have been won at London Tribunals on this.