Wheel Size Confusion

[vkmotorsports]

Hi
I am looking to buy a set of used wheels to install winter tires on my Porsche Boxster S 2001 model.

Currently, the car has 215/45ZR17 All Season Tires all around, so I am assuming the front and rear wheels are identical size of 7.5Jx17 ET50.

Now, the wheels being sold are "17x9 for the rear and 17x7 for the front".

Is that a good thing to have different size rear and front wheels for snow/winter tires ? Or does it make sense to do this for summer tires ?

Please advise.

Thanks.
VK