My stolen i-Phone is offline but continues to give me an updated location on Find My. What does this mean?

I recently had my i-Phone stolen from me around a week ago. I turned on Lost Mode and after it went online Lost Mode was activated and sounds began to automatically play on that phone. Since then however, on iCloud.com the phone has been offline. It has not been connected to the internet. Yet, when I check FindMy on my new phone, the stolen phone continuously updates its position and I can see where it was (#) minutes ago.

Does this mean the thief is actively using my i-Phone? Is my i-Phone locked and safe from being accessed? It did have a passcode and face ID before being stolen.