No, those are the stock 16" wheels for the IS300 too. Buyers had the option of 17" versus 16" wheels with no difference in price. The 2001 IS didn't have many options to manipulate. That car is fully loaded and isn't missing anything.
You can buy some nice wheels with the money you save on the used car and use the 16" for the winter.
The only way to get 16's when I bought my 01 was for the dealership to special order them. All the IS's on the lot were fully loaded with 17's. It was not until I got to Virginia that I saw IS's at the dealership with 16's.