I strongly suspect interior cells are affected by exterior cells to an extent we haven't seen before. Many of the reviews talk about "doorless" transitions to certain caves and dungeons. Imagine walking into a doorless cave in the middle of the night, finish the loading screen, turn around, and its broad daylight.
This.
I completely forgot about the whole doorless caves that were mentioned a long time ago.
If they didn't add something to compensate for the change in atmosphere on different cells then they would have made a HUGE mistake.
And if they did balance the lighting on certain parts to give you the feel of how the outside is, I don't see what can be so hard about adding that to almost every cell (excluding maybe basemants and such) with a background sound of raindrops if it's raining.