This is interesting. I felt alot of wiggle on mine, drove to the Apple Store after having the watch for 15 days. They checked it (3 people in the store + 1 technician) and compared it to the watches in the store. They all agreed that mine had more wiggle than the ones in the store. They exchanged it for a new one instantly.
All SS-models have a _SLIGHT_ wiggle, don't ask me why. The issue arises if it's alot of wiggle or not. I was afraid the waterproofing would be an issue if the wiggle was too much, hence why I went to the Apple Store.
Just my two cents.