Stationary light artifacts visible while visibility=off

So here’s something I did not expect to happen…

I have a bright colored light that will function as a strobe (i.e. it flashes ones per second). Since it doesn’t need to move, I figured to use a stationary light. Now, after my light build, the lights (or artifacts of them) are showing even when it’s off! How come? Is there any way to set this up without using a Movable light?

Here are some screenshots with the light off vs. on.