Here's my observation: Limbal rings give off actual light now. It's subtle, but look at the way the lighting around the eyes changes with and without the rings here:



However, it's only at night. Limbal rings in the daytime look a little brighter in shadow than direct sunlight, so that's where I've placed my character, but you can still tell there's no glow.



I'm assuming the glow is something that gets turned on at night in game, probably at the same time the background music switches from the day version to the night version. I think the glow is lovely, and of course, it looks much closer to the way my character's limbal rings look in the game right now. If the glow was on all the time instead of just at night, or we at least had the option for it to be on all the time, I'd be satisfied.