GP does not sound like a hikikomori; he even admits to going outside occasionally. If he wants to increase his hiki-level, he needs to reduce social contact as much as possible, and only come leave his home at hours when no one will notice him, if he leaves at all. The whole point is essentially self-imposed solitary confinement due to extreme fear/depression/social anxiety. Asking what's wrong with a reclusive life doesn't sound hiki to me at all.