How did I get updated to 9.20?

I never connected to Garmin Express because I did not want the update yet. Today I was surprised to see GC on my android say something about one of the new features but I chalked that up to android updating GC.
Now I go to workout, hit the button and nothing happens for what seems like a long time, then my watch flashed a white screen that I only caught a glimpse of but I saw 9.20 on it. I pressed teh button again and after many seconds, the menu came up and I was able to press Strength and weight train.
After I got done, I went to About and sure as bleep, my watch is 9.20. I thought the only way to get an update is through GE while plugged in. I haven't plugged in since saturday.

I do have BT and wifi on all the time and wifi only knows my home wifi. is that how this happened?