Ideas
Yes, they can also get hit by lightning as if they are outside. Or even do the watching the stars action indoors. Sims that have the indoors/outdoors Lifestyle are also affected. They basically are never indoors anymore, anywhere. Only in basements.
I have noticed the lifestyles thing, too. It affects moodlets too. It doesn't seem to affect ALL moodlets, but some. The "Fresh Air" Happy+1 from the Loves Outdoors trait that sims get triggers only outside (and not every time, but this might be intended). Sims also still get the "cooped up" tense moodlet occasionally (seems to be usually on waking up in the morning for me). So whatever governs these moodlets seems to still work. At the same time, the "pleasant chill" Happy moodlet that comes with the iceproof reward trait does activate inside and in heated rooms with thermostats or fireplaces. It's really weird. Loves Outdoors and its resulting moodlets are basegame, while ice proof must be a seasons feature, maybe there's something there? ¯\_(ツ)_/¯