Some snippets, like this, read a lot like codegolf functions.

Code Golf is about using the most terse syntax (and frankly, showing off while doing it).

This was a new syntax added to the language spec to reduce the amount of boilerplate required for common tasks.

Also, the "fat arrow function" handles "this" different inside of the function, so it can serve a slightly different function and in many event-handling cases it can be even more terse than traditional JS functions.

I am not the owner of the project, but from my point of view, brevity should be quite important. Some names could be more descriptive, though.

I agree with you, brevity, as far as quantity of code required to accomplish the goal is concerned, but too many times brevity is confused for compactness, which to me, is the opposite of what you would want with these.