So... a friend of mine and I were migrating from the official Epic Games launcher to Heroic, simply because the Epic Games launcher has horrible performance and this is no secret to anyone.
The thing is... during the migration, my friend simply took the game files that she had already downloaded from the Epic Games Launcher and imported them into Heroic. After that, she uninstalled the Epic Games Launcher and when she opened the game through Heroic... she encountered some problems. The game worked, but the high-quality textures did not stream, and she could not access screens like the buy screen (who shows when you try buy an item with real money).
On the other hand, I already wanted to reinstall my game due to some problems, so for the migration, I completely uninstalled my game, then the Epic Games launcher, then installed Heroic and finally, downloaded the game from Heroic. By doing this, I did not get the same problems as her and the game worked perfectly.
So... my question is... if you just use the Fortnite game files directly from the Epic Games Store download, they won't work? For this game, it's necessary to reinstall it through Heroic? And if so... why? Doesn't Heroic download exactly the same files from Epic Games' own servers?
I would like to have this information clarified since I want to guide another friend of mine to do this migration, but I don't really understand why this problem happened and if it is really necessary to redownload the game.