For those who haven't read it the spillers here's my reasoning as to why it can't be Kanjiro.
If Kanjuro wants to lure them into a trap and kill them then he would draw someone who wouldn't cause doubts, someone that scabbards unquestionably trust. Choosing Oden is stupid since the scabbards would immediately realize that something's wrong, especially in middle of a fu*king war, especially after seeing Kanjiro's abilities. The scabbards saw Oden die with their own eyes, convincing them that he's alive would be really, really hard. You might be able fooll Kinemon but not all the scabbards together, especially Denjiro who has been shown to be quite smart.