https://www.overclock3d.net/news/software/borderlands_3_will_not_be_pre-loadable_on_the_epic_games_store/1 On Twitter, Tim Sweeney, CEO of Epic Games, has confirmed that Borderlands 3 will not be available to pre-load on the Epic Games Store, even though Epic Games lists "Pre-Loading" as a shipped feature on its Storefront.
In a later Tweet, Sweeney stated that "It’s Complicated", regarding game pre-loading support. "We’ve released support for file preloading which is sufficient for some games, but we aren’t certain it’s up to the demands of a blockbuster like Borderlands", says Sweeney. This could be construed as a confirmation that the Epic Games Store's pre-loading feature is incomplete.
As it stands, it looks like Borderlands 3 isn't going to be available for pre-load on the Epic Games Store. Hopefully, it will be available in future AAA releases on Epic's storefront.
Personally I don't see this as a huge issue. People will still buy it when it is available.