Genetics are poorly understood and they are complex so.
Each seed is different, the genetic diversity is huge.
Even though we call something white widow, it’s only because the original white widow that was made wold famous was made by crossing plant A with plant B making white widow which was one of countless seeds planted.
So if you buy white widows and you drop 100 seeds you could see 100 different plants.
However most cannabis is actually pretty close in genetics. Often they tend to lean farther to the mother or the father, once and a whole we get a unique one and sometimes we get all unique ones.
Basically it’s all weed and the quality control is very minimal because it takes years and years of inbreeding and that currently doesn’t make most breeders more money.they make more money by putting out new products aka new strains.
Commerical growers on a start up will often drop 100+ seeds and only select one. Sometimes they will go through hundreds of seeds for years until they find a plant worth cloning.