Gidday, Welcome to the Forum.
Unless they’re staging the photo and going for the look of seldom used track, painting the top of rails is a BIG No No!! For precisely the reason you’ve given, conductivity, or in the case of painted/dirty rail, lack therof!
If you care to look through the Forum, there are a number of threads regarding track cleaning, here’s a couple…
https://forum.trains.com/t/track-cleaning/165516
https://forum.trains.com/t/track-cleaning-strategy/238321
Cheers, the Bear. 