This is new and experimental. It’s not fully implemented yet, because they have to work the whole thing out. You don’t make an instruction manual for an unfinished airplane, duh.
Furthermore, they’re literally reinventing the wheel, so to speak, in creating a physics engine. It is no small task, and you just need to be freaking patient and not act like a spoiled child not getting what they want. Sorry but you’re being a brat. The truth is without ue4 you wouldn’t even have a hope of doing any of this and you should thank your lucky stars you even have what you have.