The short version is that it's not that simple.
Most characters seem to have most of their pre-Flashpoint histories, but others are still more New 52-y, like the Marvel Family, and a lot of characters have had elements of their backstory from both timelines reaffirmed in modern continuity, with varying levels of effort at reconciling them.
Merging articles, or something similar to the way this wiki handles pre- and post-Crisis characters, might be a more accurate reflection of the current DC universe, but that would be hard to pull off and to get right.
