With apologies for lowering the tone of your well framed question, but my casual interpretation from a major credit risk project (2003-2005) indirectly advised by Siddiqi, was that the IV > 0.5 "suspiciously high" bracket was a crude sanity check flag that the predictor had an unnatural relationship with the response possibly caused by (basically) mistakes ...
"One of the attractive features of the logistic
function is the fact that it is bounded between 0 and
1, making it suitable to represent probabilities. "
"The Poisson intensity model introduced in this
article still has serious shortcomings despite the major
advancement offered by its dynamic features. First, it
is known to be unable to properly capture the ...