No one can definitely say, but there are certainly some pretty big red flags. I also don't buy into the black balled conspiracy theory that all of MLB isn't touching him just for off the field antics. I just think they probably don't think the realistic juice is worth the squeeze.
1. He wasn't even the best pitcher on his (Japanese) team last season. He was also so bad early in the 2023 season that he was demoted to the minors.
2. He's an admitted cheater (i.e., tacky stuff). Pre spin rate increase he was a mediocre / 4.00+ ERA picher.