Atwill said that Jesus is, “the only fictional character in literature whose entire life story can be traced to other sources”. I agree with him and probably so would Robert M Price.
The purpose of citing Price was because of his mythicist beliefs. Carrier's also debunked Atwill. Neither are in the scholarly consensus on mythicism. But it's irrelevant to Atwill's ideas. There are easier routes to a mythicist position than to fantasise Josephus writing the gospels for the Flavians.