SnowCub

I have 14k miles on my 2021 Mercedes GLS 450 and I think my rear tires are done. I was sliding around a lot in the rain recently. Since there are not a lot of options for tires in my current 21" staggered setup, I was thinking I should downsize to 19's or 20's. But according to the Tirerack.com website, there are no 19" wheels available for my car and there is only 1 choice for 20" which is sold out. Just to see, I tried looking for wheels for a 2021 Mercedes GLE450 and I was shocked to see 67 choices for a 20" wheel. But why? As far as I know the wheel specs should be the same for the GLS and GLE. Can I just buy GLE wheels and slap them on my GLS?