The drawing is fan made.
Oda saw it and commented as "A gathering of swordsmen". Meaning that he considers all the character that are there as swordsmen. Law is among them.
Another time a fan made a drawing with Zoro, Law, Kinemon and Brook. Oda, again, commented with "... these four swordsmen".
Like it or not, in Oda's mind Law is a swordsman. All your damage control, all your excuses, all your denial, all your mental gymnastics... still won't change that.