It's totally a glitch haha. I expect they do a state check/set a state during a combo, and because the lil KT-ling is in a non-responsive state the state isn't set correctly to him.
When you just frame the input you manage to get him to receive a command throw instruction before receiving the "in combo" state check data. So instead of refusing the command grab and doing the KT Slap, he instead does the KT grab.
Edit:
I agree with Jailhouse however, don't fix this, don't fix the d1/d12 glitch. You just released MMH and even with these both in place Zod does not seem to compete well with him in the toolset department, not to mention the rest of the cast.