It's a faulty comparison, no
MLB scrubs ever went to the Negro Leagues and dominated. While some Japanese stars came over and failed or became meh players. I still cringe at the hype over one of them who failed a decade ago as a Met fan
Really? White weren't allowed to play in the Negro Leagues. I can't believe we got to this point.
On Oh:
Oh played 110 exhibition games against major leaguers, either in October or November or during spring training. He had 338 at bats and hit for a .260 average with 88 walks for a .413 on-base percentage. He also slugged 14 doubles, no triples and 25 homers among his hits, for a .524 slugging average. Oh took ATD stalwarts Jim Palmer, Tom Seaver, and Steve Carlton (among others that haven't been drafted yet) deep.
There have been 54 Japanese born MLB players that have come to America to play in the MLB. There's currently 5 who are doing very well and have at least 1 All-Star game under their belts. 1 other has been a regular on 4 different teams and another just came over and had a pretty good year. 5 other players, who are retired now, carved out good MLB careers that include All-Star appearances, a No-Hitter, and a WS MVP. There was also a certain Yankees' star who started his career in the NPB then came over and was a 7 time All-Star.
A lot of the other ~40 Japanese players that came over weren't exactly the cream of the crop. A 30% hit rate isn't exactly a terrible percentage, especially seeing as how players weren't allowed to come over until around 1994 and the posting system forces them to play part of their prime before they can think about jumping leagues (if their team allows it).