Does the VFR > CFR conversion process create a perfect copy?

[Cornucopia]

Smartphone cameras don't "play nice" with their environment. They gather as much light as is needed for a given expected exposure, and do so by slowing the framerate (and the "shutter speed"). They can only "catch up" if light level grows to the point where they have enough exposure within the intended framerate.
Shooting a tv/monitor is not a great reference as there is always a certain amount of light coming from the screen, and the dynamic range even these days isn't nearly as variable as real world, so light is likely be close to sufficient except in the most dynamic of scenes.
That's one of the pitfalls of using a smartphone (a very few models excepted). Of course, it would happen to any cam sensor that was so small - it just doesn't get the same amount of light that larger sensors get.

Scott