When I said "the whole game engine part", I was referring to the usage of the engine at all. The whole engine obviously isn't loaded, but there's further abstractions and initialization code compared to using CEF or the Edge web view directly.

I'm simply saying that it's a waste of resources to require loading or initializing any other part of Unreal Engine (including the component loading code!) when they're only using it as web view.

I'm also not saying any other storefront is better. Steam is a bloated pig that half uses CEF and half uses Valve's own proprietary GUI library, and the various other Electron-based publishers' launchers suffer from different but equally stupid problems.