nowdays is very difficult to make specialized code because of the immense complexity of the hardware. So most libraries and features end up being generic because the author have no idea how the users will make use of them.
Take Unreal, its used for way more than making games and as a matter of fact EPIC even encourages it. For example is quite popular in architectural visualization.
Even the old BGE was generic enough to be used for a wide variety of tasks. Most likely interactive mode will be even more generic. Interactive mode will focus purely on making Blender interactive and not on game engine stuff mainly because Blender already has many of the ingredients of a Game engine. Real time rendering through Eevee, physics, particles, animation, python scripting , image and video editing, compositing, audio and much more.