I believe he withdrew after getting JSF's approval and JSF already promised him the spots to 4CC and worlds. Otherwise, he would've chosen to compete to earn the spots even if he is sick. He is someone who competed after the collision in coc and right before his surgery in 2014 national, so he could qualify for GPF and earn the worlds spot after all.
JSF approves of his withdrawal because JSF actually doesn't want to force their top skaters to do Asian games. They only issued that public statement requiring their national champs to compete in Asian games because they are the host and the public expects their best skaters to be at Asian games. But JSF also knows none of their top skaters wants to compete at Asians Games if that means missing out on 4CC next year. (Asian Games has no value to any top skaters or to the skating community. Sorry, but this is true.) If Yuzuru competes in national and loses, and thus not compete in Asian games, or he competes in national and wins and choose to not compete in Asian games, either way it makes Yuzuru look bad in the public. Letting Yuzuru withdraw is JSF's way to let Yuzuru skip Asian Games and compete in 4CC without making him look bad in the public.