But that's what I want explained why is more blood beneficial for a person's forearm?
I don't feel like I am lacking blood flow during my daily tasks in life. Can "extra arm artery mutant guy" out-compete me in a specific task so critical it means his genes are more likely survive than mine are?
Worse, Wikipedia claims it’s easier to commit suicide by slashing your wrists if you have this artery (https://en.wikipedia.org/wiki/Median_artery), and https://radiopaedia.org/articles/persistent-median-artery-of... says it can be a cause of carpal tunnel syndrome.
I don’t see how either could be an evolutionary advantage.
The most likely answer is that natural selection isn't directly driving this specific trait.