Amtrak and NICTD stops in Michigan City aren’t really close to each other.
If you’re going to take the Wolverine, just ride it to Chicago. There’s no real point to introducing a complicated transfer (unless the specific adventure is part of the point of the trip).
As it stands right now, there’s only one train a day running, and it’s the early train (351) which doesn’t even stop in Michigan City. Even under full service, 351 is the only Detroit train connecting to western LDs, so even if it was potentially advisable to transfer to NICTD, it wouldn’t be possible. Further, if you’re connecting to a western LD, why complicate the itinerary by getting off an Amtrak train, making a mile-and-a-half transfer to the South Shore to ride a slower train to Chicago (which doesn’t even factor in how much time you’d have to wait for the next South Shore train), and then make another mile-plus transfer in Chicago from Millennium Station to Union Station? Outside of the NS being shut down from Porter to Chicago, there’s almost no scenario in which that makes sense.