And hitting free agency as a 25 year old (see Yamamoto’s 13 year contract) vs as a 29 year old.

3 of those 6 years will be arbitration and better than league minimum, but not close to free agency either.

He could also lower the chance of injury in Japan by sitting out and mostly just training on the side.

Financially it doesn’t make sense at all, but like Ohtani he may just be motivated by being in the majors.