DJ77
Surely that's a question for the aerod and systems dept at AI. This wouldn't be a matter of 'stall' as much as initial buffet onset. Pilots wouldn't have much if any experience of flying into that AoA regime during cruise, surely, to be able to assert 4.2 is too early, 4.5 is about right. These things are figured out from detailed consultation of test-flight crew/flight-test engineers and examination of buffet/maneouvre limits of the wing from plotted Lift~Drag~PM/Mach boundaries.