as opposed to..... just loving typing it all out?? because a scratch-like system with event blocks somehow.... is bad? because?? reasons??? do you understand that doing it this way makes it extremely easy for non-programmers to pickup and get things done without having to learn an entire coding syntax/command list, while still being able to make complex scripts?
There's a fundamental flaw with the idea behind scratch which is that syntax is infinitely more trivial than understanding logic and solving complex problems, which encourages people to just slap stuff together like lego and pump out utterly useless logic. It's useful for getting kids interested in the idea of programming but it's not actually a useful tool for programmers.
Obviously they'll have a way to convert between baby megablocks visual coding and regular code, because that would be trivial compared to creating an entire language within ue4 runtime and integrating it with every single game system (this sounds like a nightmare but you gotta do what you gotta do for those really really awesome UE4 Screen Ambient Space Ray Occlusion Spherical Tracing Aberration Volumetric Reflection Real Time Floating Point lego graphics) and after that it will be easy to just load those scripts from a file into the game for easy distribution.
I still wouldn't really call this modding though because you've just been given metered access to game behaviors and you're not actually "modifying" the game. Until it's able to support things like classes and inheritance and polymorphism it really is just fancy events, and don't get me wrong that's very impressive on it's own. But I'd be more interested to see how they are handling things like arbitrarily putting new assets models and sounds into the game, replacing existing assets, ect. Blockland was REALLY good at this once port distributed a solution for dts. I imagine this is where the Epic™ Games®™ Epic™ Launcher® People's™ Democratic Engine™® 4™ (50000 Tb) thing is going to come into play
scratch sucks though they should implement something like intellisense