The EFIS Comparator constantly monitors both sides and looks for disparities between the two.
Is this a comparison between the PFD displays or is it between the right and left attitude sources? Logically it should be the attitude sources, and if both PFDs are set to the same source for some reason, the warning chime may sound, but it might be lost in the confusion over what just happened.
Unless the accident investigation team finds an external source of data (such as radar glints on a primary radar) that gives them at least a few hard roll attitude data points, they will be just as lost as the accident aircrew was on what the actual roll attitude was.
Without discovering a valid source of attitude information, the probability of the crew recovering from their initial departure was nil. Is it really necessary to know the twists and turns of this aircraft on the way down to learn the necessary lessons from this accident?