Q: Personal hotspot activates when iPhone is connected to computer

This morning when I came into my home office I noticed that the blue bar indicating the personal hotspot is active on the top of my iPhone. I thought that was strange since I hadn't connected to my phone's personal hotspot, and my Macbook Air was not showing that it was connected to the hotspot. It took me a while to figure out what the issue was, but eventually I found that connecting my iPhone via USB to my MBA seems to activate the hotspot on the phone (without connecting my MBA to the hotspot).

This isn't expected behavior, is it?