T-Mobile rolls out Samsung Galaxy S9 update which improves face unlock, other features
However, this particular update brings improvements to some of the phones' features such as face unlock and camera. The official changelog mentions the update adds stability improvements to the camera, as well as bug fixes.
The update file weighs in at 260MB, so it really isn't a sizable download. For the tech-savvies, the firmware version you should receive on your Samsung Galaxy S9 is G960 USQU1ARBG or G965-USQU1ARBG on the Galaxy S9+.
T-Mobile has yet to update the phones' support pages with information about the new firmware, but this is likely to happen in the next few days. In the meantime, enjoy the improvements that Samsung is bringing to its new flagships.