The art mode dimming is very good, it has tricked every single visitor I've had in my living room, they always say nice painting. Then their minds are blown when it's revealed it's a TV. It's very convincing at first glance.
Problem is showing personal images, it does not do as good of a job. I think it uses the same settings as other inputs.
Not applying art mode to arbitrary user pictures removes the risk of them making art mode look bad, when art mode is pretty much the main reason to buy this TV over another.
Well, that's one expensive toy expense saved I guess.
I'm not sure what 'looking natural' for a television screen might look like. Naively, if you wanted the television mode to look more like moving pictures, I'd think you'd have to figure out a way to knock down the refresh rate considerably. 15Hz ought to do it. If you're asking me if it just adjusts the television brightness to surrounding lighting conditions, I don't know, but it feels like art mode is doing more than just adjusting brightness (though possibly I'm wrong here and brightness is just much more convincing than I've experienced in the past)
Take this with grains of salt as I don't own one, don't know the interval, and couldn't guarantee that it isn't bricked without an internet connection, though I find that highly unlikely.