The major reason for a non LBA valve body is to eliminate overlap in the 1-2 shift. In an LBA valve body the low reverse band has to release while the intermediate band applies. If the release of the LR band is too fast or the INT band to slow, you will get a flare in the shift. If the opposite is true, you get a bind up. Even when it is timed perfectly, there is still a short period of time when they are both applied and cause a slight delay in the shift.

In a non-LBA valve body, the sprag or roller is holding the LR drum and when the shifter is moved to second the Int bad applies and the roller clutch unlocks as it is turning in the direction in which it freewheels so the release is immediate. No overlap to deal with.