Its not a free win as ive said 1000 times scorpion and batgirl dont hard counter those 3. They counter zoning those 3 arent the only ones with zoning. What do you mean never meant to rely on? Deathstroke has some of the dirtiest mix ups and his own vortex. Cyborg has among the highest corner damage in the game sinestro has unblockable set ups and resets. Batgirl and scorpion rely heavy on their counter zoning i can take that away by not zoning.
That's all nice, lets see...
KF has better mix-ups and doesn't do crap for damage.
Cyborg has the highest corner damage? Level 3 venom Bane says hi while he does the equivalent of Cyborg's damage in one simple BnB string. Also Superman does the same if not more damage and is all around better.
Sinestro has unblockable set-ups IF he manages to corner you.
You can not zone, you still only have half a kit and all the tools you have aren't made to be stand-alone.
Want mix-ups and dirty damage? Pick KF.
Want corner damage? Pick Superman
Want unblockable set-ups? Good luck getting to the corner or even charging trait.
Batgirl and Scorp only use one attack for counter zoning, everything else is for general use. That means it takes them one attack to get rid of half your kit and you are forced to play footsies with characters who can beat you in that field because they can use tools when you can't. You aren't gaining any advantage by picking those 3 when characters take away half the kit. No matter how you try to twist it, your options that you have left aren't going to beat out a full character. ESPECIALLY not batgirl who sits in a comfortable spot in S tier as it is because of her insane pressure game.