The aircraft they are getting at in the article is the ATR-72 (or perhaps, misguidedly, the Q400). They would require an extension to operate effectively (or at all). Probably something like 1700 m at a minimum.
No, they wouldn't. ATR72s and Q400s routinely operate out of London City (1200m) and Gueurnsey (1483m), to name but two. You can normally lift a full load out of both (from memory - KLM UK used to lift full loads out of London City, but they they were only going to Guernsey).
At 1470m, PP is plenty long enough, so I guess that argument is academic too...