Hi Andrew,
That’s not quite right. It works a bit different from what you said.
Direct light and indirect light have different density in real life. That’s why when you put a flashlight behind your hand you see your hand getting a red tone, and when you remove the flashlight from the room, even though the room is fully lit by indirect light, you don’t see that red tone on your hand anymore. Let’s take a look at the example below, I believe this helps to better demonstrate the issue.
This is a room lit by indirect light, then there’s a flashlight on the table, and a hand covering the flashlight.
http://uupload.ir/files/ifuu_12.jpg
What you said above essentially means that if we remove the flashlight from the picture above, the hand should still have that red tone because there are still indirect light in the room hitting the hand. That’s wrong because i.e 5000 photons from flashlight hitting the hand is not the same as 1000 photons from indirect light hitting the hand, indirect light is sparse photons and not a photon source focused on one direction like a direct light source, hence, indirect light leaves far less noticeable. The reason you don’t see your whole body being red under overcast sky is because all that indirect light does not equal to the direct light from a tiny flashlight that makes your hand look red.
As you know, the correct behavior would be for the hand to lose all that red tone as soon as the flashlight is removed. Which means, your green looking ball should lose all the green SSS color as soon as the directional light is removed, and under the skylight it should look black (as your base color is) and with a very, very hard to notice dark shade of green to it.