In most cases, I don't think so. With masturbation, you're at least having sex with yourself. Asexuality I believe means to have no sexual desire at all (admittedly, I have not looked at a dictionary definition before responding to this post, so anyone, please correct me if I'm wrong).
I would think someone who doesn't want sex but who masturbates still has sexual desires. Perhaps the hypothetical person in question just prefers masturbating to sex with another person, or has a psychological hang up about sex, and so prefers keeping it personal.
if you are asexual it means you reproduce without another individual
it has nothing to do with your sexual desires
asexuality in humans is a sexual orientation.
It means they are into porn. They don't want to have to involve another actual person in their sexual gratification.