I would point out that the study which appears to be the closest thing to a tiny seed of truth to the tank story (Kanal & Randall 1964) actually did balance its

I would point out that the study which appears to be the closest thing to a tiny seed of truth to the tank story (Kanal & Randall 1964) actually did balance its photographs by construction, by subcropping large aerial photographs to have tank/no-tank sections and training on that. That necessarily controls for time-of-day, weather, luminosity etc.