Why does Gaussian blur in illustrator have a phantom outline (halo)?

Question

Adobe Illustrator

I haven't figured out what else to call it. In general, look at the screenshot.

Document 1000x100px. A simple circle filled with black in RGB mode.
Up to a certain point, it’s normal, here:

Well, then what is on the first screen. Is this normal behavior of Gauss or am I missing something?
Just in case: GTX770, win 10 x64, Adobe Illustrator CC 2018

Answer 1

Go to menu Effects -> Document raster effects settings -> Add [number] around object.
For example, here is a circle with a 24-pixel Gaussian blur, default settings:
* * *
But with the notorious settings, where I entered 128 px in the [number] input field (I took the number from the ceiling, the point is that it should be significant more blur value)
Voila.