Yes it is due to relativity. It is also technically time traveling. Relativity and Time Travel are linked at the hip. But if you want to argue with Physicist Dr. Michio Kakua about that, be my guest. (I prefer discussing Schrödinger's cat myself).
As Dr Kakua explains it technically the satellites are time traveling. Just like our astronauts who went to the moon and came back to earth 10-8 seconds 'younger' than us who stayed right here. So they 'time traveled'.
>>So they ‘time traveled’.
No, for them the progression of state change was simply slower due to the larger inertia created by the increased Energy/Mass within their accelerated inertial frame.
When time is observed to be a derivative function of the localized rate of state change, the whole notion of “time travel” becomes nothing but fiction.