I was just going to post the exact same thing. When I enable hotspot on the 7a, wifi disables automatically. When I disable hotspot, wifi gets re-enabled automatically.
On my 6a, I can have hotspot and wifi enabled at the same time (enabling hotspot does not disable wifi automatically like it does on my 7a) which allows me to share my wifi instead of cell. Seems like a bug or some hardware change that causes it, perhaps?