VFX Editor not using all Atlas texture UVs?

Do VFX made with the editor not support using all of the UV spaces of a
texture atlas? When I go to plug in my custom texture for a visual effect, I
can tell it to use an Atlas texture, then specify it as 4x4, which is how my
sheet is set up, however it only uses the second texture on the top row. It
does not use any of the other UV spaces. Is there anything specific you have
to do here to get Atlas textures to function correctly or is it just a bug? I
see that some of the default VFX even use atlases, but I haven’t checked to
see if the effect textures are selected randomly or if it’s the same UV space
repeating like it is for my material. Edit: I found the SDK doc about the
AtlasPlayer and got it set up as directed, so I suppose that takes care of
this topic. However I opted to not use the player as it was making my fire
effect really choppy no matter what FPS value I assigned. And the higher the
FPS value, the faster the sprites spawned.