No genetic bottleneck proves no global flood

So the arc coulda happened and not shown a bottleneck?

Don't emphasize the "are" when you don't actually know.And the dark fur mutation is an excellent example of a deleterious mutation. It is clearly very deleterious and, being dominant, subject to strong selection pressure. That is why it is constantly stripped out of the populations.That is, deleterious until there is a nearby dark lava field. Then suddenly it is extremely beneficial. and by what magic did one of them appear on one lava field and a different one on another but not both on the same field?

The point is that a mutation (or any combination of genetic material from whatever source) that produces a specific body form is not any of neutral, deleterious or beneficial in and of itself. (this excludes ones that produce a non viable embryo and such like of course)Dark fur is a phenotype and so is light fur. If there were no hawks flying around the both of them would be neutral.Any genetics that causes a dark furred phenotype is very deleterious in the light sandy areas and very beneficial in the dark lave areas.So if a mutation does cause a genetic change to dark or light it isn't by itself either bad or good. It depends and that is true of many different genomes.The question of whether is it a mutation or not has much evidence suggesting that it is.