Oh dear. Dont go there man, it ends up deep into looney town, we have had multiple topics on it over the years.
Flickering and inconsistencies in graphics rendering do indeed happen and its a combination of how gpu handles processing and how the engine works. Countless tricks are applied to optimize performance, this includes numerous ways to simplify detail and apply LOD. There are techs like ambient occlusion in numerous forms that can flicker in shadows for example. The list goes on and on, and not everything is as refined or visually correct as you would want.
That is the long and short of it really. Shrug and trying to unsee this is really the easiest approach and otherwise, you need careful analysis per game version, GPU, driver versions... every time...