>Google Fi ... is an MVNO telecommunications service by Google that provides telephone calls, SMS, and mobile broadband using cellular networks and Wi-Fi. Google Fi uses networks operated by T-Mobile and U.S. Cellular.

> A mobile virtual network operator (MVNO) is a wireless communications services provider that does not own the wireless network infrastructure over which it provides services to its customers.

T-Mobile owns the wireless network infrastructure, so an MVNO cannot be “by T-Mobile”, in any meaningful sense.

i.e. as opposed to consideration by you, me, or Wikipedia articles