Forgive my brief rant:
Peter King is a fatuous blowhard who is obsessed with himself. He fancies himself as a connoisseur of many things, including coffee and football. He really is terrible, given to making obvious statements and coloring them as insight, and making it look like he has really close personal relationships with most NFL players. Accuracy is of course an indispensable characteristic of a successful quarterback, as is "pocket-sense" - feeling & reacting to pressure, avoiding contact, etc.
Now then...
Completion percentage can be a deceiving metric, stat-wise, especially in west coast offenses. I think downfield accuracy -- completions of 15-20 yards or more -- is a better measure than just straight completion percentage, when it comes to being considered an accurate QB.