I have no idea why AF447 "did not switch to Abnormal Attitude Law", especially since the BEA release appears to indicate that the parameters that should cause this were in fact exceeded. So, if it didn't - why not?
The only parameter to trigger Abnormal Attitude Law which was experienced by AF447 was the Angle of Attack - however before the AoA reached the limiting value, the air data was disregarded as unreliable by the system. The other parameters required to trigger Ab. Att. Law (50/120 degrees pitch/roll) were never met.