This may look like a strange transaction to you, but I suspect it was a pre-arranged thing, perhaps pursuant to Kawasaki’s minor league contract, or perhaps to save a little money. Because otherwise, you are correctly surmising right now, there would be no reason to put a guy, who is already on a minor league deal and already heading to AAA Iowa, on the 40-man roster and then option him to the place he was already going.
You may recall that last week, Kawasaki was briefly released and then re-signed to a minor league deal (again, it was a procedural thing – he was never going anywhere), so there are clearly some contractual things going on here.
With Kawasaki on the 40-man and with available options remaining, the Cubs can now freely bounce him up and down from the big league team to AAA as necessary this year. Given his defensive and baserunning ability, that’s going to be a nice luxury if injuries pop up. He’ll see time in Chicago this year. There’s little question of that. And it’ll be fun. A lot of fun.