I understood that; I also use a dashboard magnet mount for my own iPhone. But the two topics are actually conflated by what might be a non-obvious issue, so I suppose I can see why you might not have thought I was addressing his particular issue -- so to be more direct:
The answer to that question is almost always guaranteed to be "no" when wireless charging is involved, specifically because metallic content tends to interfere with wireless charging technologies, Qi included. Thus, that little stick-on metal disc that comes with the magnet mount is still necessary for those of us who prefer magnet mounts... which means that for AdventurousJosh to take advantage of Apple's new Smart Battery Case, he is going to have to either find a second disc to put on the case, or he's going to have to remove the disc from his iPhone and find a way to adhere it to the case.
Here is an example of the charging issue I'm describing: I happened upon a Qi charger the other day, and of course, I promptly tested it out with my iPhone X. It just so happens that my own metal disc was transferred over from my old iPhone 6, and therefore isn't sticky anymore; thus, it isn't actually adhered to the back of my phone, but held in place by a very thin silicone case. With that disc in place, my iPhone X would not charge wirelessly, but when I removed the disc from within my case, it charged just fine.
Thus, Qi charging and magnet mounts are generally an either/or proposition; you can't really use both simultaneously because of the inherent incompatibilities.
