Hi Andrew,
As I stated above
Yes, the story can be a bit confusing, but it is important to understand that these two dynamic text elements are not exactly the same. The Map Series (DDP) Attribute element is legacy functionality from ArcMap (Data Driven Pages) and only works with the index layer of a map series. Table Attribute dynamic text, however, can work with any table in the map and does not have to be part of a map series.
Although, as you state, the Map Series (DDP) Attribute is limited when compared to Table Attribute dynamic text, this "simple" text element satisfies many user requirements. Many users like the simplicity of this option - they just want to add an attribute value from the index layer without any changes.
I'm sure you would agree that if we eliminated the legacy option some people would complain that they have to go to a new, more complicated dialog to do something that was relatively easy in a previous version of Pro. IMHO, I think more people would be complaining if we took the index-only dynamic text options out and forced people to use the Table Attribute option. If you just want to add the name of the page I think the legacy way is easier.
Also, overlapping or redundant functionality is not unique to dynamic text. After all, how many ways are there to add layers/data to a map? Should we just pick one and force everyone's workflow to conform? Generally, we try not to change existing workflows and we deprecate functionality when we think no one, or very, very few are using it. We do not believe this is the case with Map Series dynamic text.
This is the best answer I can give you to "why not eliminate one?".
Tom
