I experienced one encounter with severe turbulence on a 767-300, and while we experience some erratic airspeed info
Did you read the link?
There is a very big difference between 'erratic airspeed info' caused by turbulence/sheer and the textbook definition of unreliable airspeed.The LOT aircraft experienced 'unreliable speed' in the textbook sense.
While the problem was initially resolved as they descended through FL280 it's interesting to note that the problem reoccurred much lower in the descent at around 16000ft.
They had overspeed warnings followed by stick shaker which are indications consistent with a blocked pitot/static system which has led to several fatal accidents including:
Aeroperú Flight 603 - Wikipedia, the free encyclopedia
Birgenair Flight 301 - Wikipedia, the free encyclopedia
I would have thought that bearing in mind the recent interest in unreliable speed problems that this incident would bear further scrutiny.