Ok, it makes sense now. I should clarify that the TCB can't issue a "brake" command to an RC speed controller, what we call brake is actually just "stop." Most RC model tanks have so much internal resistance in their gearboxes that as soon you remove power from the motors the vehicle stops immediately.
Now some RC speed controllers do actually have a brake functionality built in to them but as you discovered the TCB may or may not utilize it. Speed controllers used for RC cars typically have two modes which RC car guys call "blinky" and "crawler" (blinky because an LED on the speed control usually blinks in this mode). If the controller only has a single mode it is usually blinky. In blinky mode (used for race cars and such) the ESC has a built-in brake function which is activated by moving the throttle in the opposite direction of travel, the consequence however is that to change direction you have to "double-tap" the throttle: move in the opposite direction once to brake, return to neutral, then move in the opposite direction again to reverse, sometimes after a delay.
The TCB was designed to take care of all this itself in order to give the user simple control through OP Config of how this works (which is why we recommend using "crawler" mode on the ESC, in this mode the ESC does whatever you tell it without delay, and then the TCB can decide if delays need to be introduced). But of course this assumed that your model will stop immediately when power is removed.
In your case it seems your speed controllers are in blinky mode and if we remove the change direction delay on the TCB you are able to brake by using the double-tap method intrinsic to your speed controller.
Now if you were using something like the Pololu or our own Scout serial controllers, those do have explicit brake commands which we can send them over the serial port so in that case you can configure OP Config however you want and they will still literally brake when told to brake, as opposed to just stop (the Sabertooth doesn't have this ability).
I apologize for the confusion and assumptions which were not always clear, but in the end it sounds like you have found a workable solution! I'm glad you're enjoying the project.