I think it's down to your internal units, and also because the "Artist" atmospheres haven't been reworked to use the new internal unit options.

Dunno if you can change it in your version but set 1 Vue unit = 1 meter. Atmospheres and indirect lighting will be "real world accurate" this way, this is the best option for, well everything but the "Spectral sunshine" collection. These atmos have an Aerial Perspective set to 10, which is fine if internal units =0.1m (the old internal units), but if your internal units are set to 1m, then you need to change the AP to 1.

For some materials, you will also notice they can look odd. Simply change material size to 0.1, and everything will be back to normal.