There is currently a buffer in place to account for accidental TKs, you can TK 1 time in a match and not face a penalty. Accidents happen.
With the change, you'll now enter a special sanctioned status after that 1st TK, so now you won't even be able to damage your teammates, let alone TK another person. So there will still be a buffer for accidents, but now that 1st TK is not completely "free".
It's not a perfect, fix-all solution for toxicity but it is the next step that the team is implementing in the process.