joy ride:-
<< IF >> one or both of these had been a contributory factor, and assuming substantial recovery of wreckage, would the investigators have any chance of finding evidence of it? Particularly as a windscreen cracked by altitude/pressure changes might resemble one cracked on contact with water.
Without going into the microscopic details, I would reckon a fracture attributed to internal forces (failure with cabin pressurised) and one due to external forces (impact with water) will be pretty evident on close examination.