I think its done in recognition of the fact that people who live in cities are frightened of the dark.
They associate it with danger.
Which is weird, as a Home Office study in the 90s found that if you turned down street lighting in an area the crime rate dropped.
Also, the report is odd. Why are the mags referred to as 16:00 and 22:00 and not 16.0 and 22.0? Didn’t anyone proof read it? Almost as if the author confused sky brightness with times. Hopefully, no AIs were involved in the authorship.
Also interesting that the sky brightness value for E0 changed in 2019. In which direction?