The duplicate data isn’t necessary anymore when installed on SSDs but a bunch of games still have it.

Helldivers 2 on PC as an example went from a bloated 150+ GB install down to less than 40 GB at some point when they found out that the duplication both wasn’t helpful for the vast majority of PC players and it didn’t have the impact it used to. Now it is comparable to the console install, which was always smaller.