I get your argument, it just doesn't wash when you really think about it. The servo doesn't "see" which lever it's pulling on. Once it stalls, it stalls...front or rear. Weren't you talking about how the servo horn would twist the servo and load it sideways? If that wasn't you or I misstated your argument, I apologize.
At some point, without the EPA set properly, if you held the brakes full-on (stalled and still trying to go further) for some extended period of time, you'd probably end up burning out the motor, but that has nothing to do with front/rear brake bias.
That's what happened to Jerry's old JR servos. Turn off the radio and the throttle would go WOT...leave it that way for a while and it would smoke the motor. I think that you wouldn't have that problem with a properly set failsafe or a Spektrum.