Flashing other carriers' or International firmware, and LTE bands

I understand that it's possible to flash firmware from other carriers, or international firmware, on a T-Mobile G6 Edge, and that it will work, albeit with some glitches that can be patched. What isn't clear to me so far is whether flashing these firmwares has any effect, positive or negative, on the available LTE bands on the device. For example, would flashing AT&T firmware on this device enable bands 29 and 30 (which the actual AT&T variant supports), or is that a hardware limitation or some kind of deeper code that is not addressed by a typical firmware flash?

DISCLAIMER: I've searched. Lord, have I searched. All I could come up with was stuff relevant to earlier devices with different SoCs or whatever. If there's something obvious I've missed, please point me there, and feel free to laugh at me while doing so.