Does anyone know why there's that skip brush in the elevator logic instances? I'm editing the elevators and I don't want to delete it if it has a purpose.

To be honest I always thought that was sort of a "guide" to make both, the "_logic" and the "_base" instances coincide perfectly... Take into account that those brushes are outside the map and after the compile they will simply be removed

there are often skips in valve instances; probably to make it easier to move around or something.
Because they are deleted during vbsp (the first step in compiling)they don't serve any purpose except for aligning stuffs.