If they continued to fight then it's safe to say Hanzou would have won. Technically he did defeat them in the sense that if they hadn't stopped, he would have been the victor. Otherwise Jiraiya wouldn't have praised him as much as he did. You could say Hanzou defeated them, but he didn't win.
The only reason he spared their lives was because he said that Konoha would win the war in the end anyways so it would have been meaningless to kill them. Even more so since they were the only 3 left alive. Hanzou congratulated them and offered to spare their lives if they promised to go by the titles of Sannin from that day on. I'm sure Hanzou wouldn't have used the word "spare" if he wasn't able to kill them.
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You are making a huge assumption... so
NO.