The Hall of Fame index was designed to measure fitness for the Hall of Fame. That seems fairly straightforward and obvious, but some might be tempted to read too much into the numbers. While it does provide the opportunity to rank order players, it wasn’t designed for that. I suppose one could use it as evidence for their own rankings, but it is not meant to be a definitive word on the subject.
What we are looking to do is compare similar players in terms of value. All players arrive at their value in different ways, but there will always be similarities.