iPhone presence test - good and ‘huh’?

Background: I tried many ways, back in the day, to utilize a ‘burner’ Android that had no SIM as an arrival sensor. Using only WiFi, it worked occasionally. Which of course means it was useless for the role.

Fast forward to today. My company has foisted an iPhone on me. So I set it up, and used it. It worked great! ST knew when it left, and knew when it returned and ran the routine to unlock my front door and turn on the front door light (as a signal to let me know the routine fired). Now one day does not a good test make, so I will continue the test over this week. But so far, so good!

What’s perplexing is this: I took my ST arrival sensor out of my work bag and left it home today. (I just checked; it is not in the bag. Indeed, it is in the dresser drawer where I put it.) Yet when I look in ST, the history of that sensor shows that it left the house at 7:31am today and returned at 4:15pm!

Has Smartthings somehow equated the sensor with the phone?

PS - I know I have lots of questions and issues here recently. That’s actually good; it means the system is worth exploring. For awhile I had kinda given up on it. But it’s now mostly (aside from device reporting time issues) working, and doing some things better than before.