WebGL Effects Boosting Performance

While playing around with optimization using a simple test bed with 600 sprites bouncing around the screen;

[viewing in Chrome on the desktop]

I noticed that with no effects, I'm getting about 44 fps.

Now after adding an effect like "Brightness" to the entire layer, I get a fairly solid 60 fps. Now Brightness is set to default 100 meaning it isn't changing anything visually.

Any idea what's happening here?

Weird! Could be a graphics driver issue. Obviously it's not logical that this is happening. Maybe it's forcing webGL when you're using effects, but reverting to canvas2D when it's not?

There's an easy way to find out, just have a text object set to display the 'renderer' system expression.

webGL in both cases.