He hit .246/.355/.487 literally a year after being drafted which is frankly pretty insane. And the only reason his line was that "low" was because he hit .143/.213/.268 vs LHP. He hit .272/.392/.544 vs RHP... in his first showing vs MLB pitching... with very little time spent in the minors... To put that into context, Kris Bryant who was older when he debuted hit .284/.376/.499 vs RHP(the better of his two splits). And while you'd like to see him hit lefties better, Rizzo at 23 in 2013 was still hitting .189/.282/.342 vs them 2 years after his initial debut. Schwarber was 22 last year.
Long story short, if you want to take Rizzo or Bryant over him I think either is an interesting debate. However, it's not as unrealistic as you're making it sound. Schwarber's ability to come in and just hit with almost no time shows how good he is. I made the case last year that it's possible Schwarber ends up being a better hitter than Bryant. I stand by that though admittedly that was before Bryant substantially dropped his k rate. And whether or not Schwarber is better isn't really the point of my argument. My argument was more his bat is Bryant level of good which basically makes him a top 5-10 hitter in baseball. People don't destroy the minor leagues as hard and quickly as Bryant and Schwarber did. Their performance in the minors was an order of magnitude from "good."
As for ARod's comments, he knows hitting. As I said, I think you can make a case Rizzo/Bryant are better but both have weaknesses. Bryant size makes it difficult to cover all of the plate and as such he's had K issues in the past. Rizzo is a hell of a hitter but he doesn't have as much power as Schwarber and overall good pitching still can beat him as seen in his post season slump to start the post season. So, I think ARod's argument would be more from a potential stand point he feels Schwarber has fewer weaknesses than those two. And honestly, are there even 5 guys in the majors who could miss 2 months of a season and come in hitting like Schwarber has? And Schwarber has missed over 5 months.