I will admit that when I first heard of the incident I assumed it must have been the static vent covers which were left in place as normal airspeed readings would be given until the aircraft was climbing
In the 737 Classic simulator, the indications of a captain's blocked static vent are quite dramatic after lift off; but not before.
When the co-pilot calls "Positive Rate" (his static vent is OK), the first thing noticed is no movement of the captain's main altimeter and his IVSI. Yet we have often seen the captain calling for gear up without confirming his altimeter reading, simply because he is reacting to a call from the PM. A few seconds, later a windshear warning sounds even though there is no windshear. That warning is because the captains airspeed indicator stops moving and starts to go backwards fooling the system into thinking a loss of airspeed is a likely windshear.
With the aircraft climbing normally, but with captain's airspeed indicator needle steadily reducing due to the blocked static vent, (and no movement on his main altimeter and IVSI), eventually his stick shaker actuates and the ASI gradually falls to zero. Unless the pilot has seen this phenomena during his simulator training (and many have not), there is guaranteed confusion as to what is happening. In other words a grand WTF moment. A quick check of the ground speed reading can ascertain the problem and decisions made.