The operators brought this on themselves. There is no standard definition of 5G, even though the industry knows the rollout of features will be in waves.
Does 5G for T-mobile technically mean exactly the same thing as for Verizon? Probably not.
Verizon is the only carrier with mmWave 5G / Ultrawide Band. Their "5G Nationwide" is what T-Mobile and AT&T have, while only AT&T has the "5GE" abomination which is just 4G LTE.
Does 5G for T-mobile technically mean exactly the same thing as for Verizon? Probably not.