Im curious, where does it say 'once a balk, always a balk?' I'm not familiar with this, but will gladly accept guidance here.
FED allows for umpire consultation when a decision could be in conflict with the rules. If your partner was absolutely sure that he saw F1 step off, then F1 was legal. IMO that's a rules interp, not a judgment call.
Now whether your partner was smart in offering this info, in light of the storm you both knew this would cause, is another matter....
I have never seen a game where a balk call was reversed...but I have a small set of data points
As you allude to, this is a sh*t sandwich either way. Once you 'consult', somebody's gonna tossed no matter what.