ttse:
Depends entirely on the type of spin and rate of rotation. A deep-stall with slow rotation (i.e. flat-spin already discussed lots)could be a better all-around fit.
Well, there are a couple problems with that, still. Note, I am not discounting entirely the possibility of a spin. I am just saying it is not consistent with the findings of the report.
If you had a spin from altitude, I would expect the plane to hit at a near vertical vector with very little forward/backward acceleration. Also unless the rotation was very, very slow, the sideways inertial forces would still be a major (rather than minor) component to the tail failure. However the report found that the rudder failed forward with a slight left-ward twisting element (it is possible that this element could have been sufficient to throw it clear of the fuselage).
At 4 secs per rotation in a flat spin from altitude, I would expect sideways and forces to be a substantial fraction of the vertical forces and the forward deceleration to be negligible. Hence the VS would have failed sideways (perpendicular from the fuselage) with perhaps some other slight vector added representing what little was left of the original fight vector. Remember that the VS is close to the extremity of the spin, so the centrifugal forces are very high there.
On the other hand, in a low altitude stall, we would expect strong forward and vertical forces, along with some minor twisting as the airframe hits the water not quite level (due to wind). This seems most compatible with the findings to date. Not that the findings are infallible at this juncture.
The basic issue is that, absent air resistance, an unpowered fall from a specific vector will be largely parabolic (roughly comparable to a plane in flat spin, though a spinning aircraft, depending on wind, might generate sideways Magnus-effect lift, changing trajectory, but shouldn't be that substantial in a large airliner). However air resistance flattens this parabola, resulting on an even more vertical impact and less forward velocity. I would expect that if you dropped a rock out of a plane at FL350 and mach 0.8, it would impact the ground nearly (though not quite) vertically.
Hope this helps.