First of all that is not how reports works. If they did loads of innocent people would be ban, and screw up the whole system. One report is just the same as nine reports (assuming everyone reported teammates and enemy team) all a report does is check the game in question. In this case because someone reported you it checked the chatlog and saw you were toxic.
It would have been the same if you reported them as well. But also remember that everyone is on a different space when it comes to punishment. If you mess up in one game (slightly toxic) the system would see it as a "bad game" and probably do nothing out it. It becomes a problem when you do it consistently, thus getting reported and having the system constantly checking your toxic chatlog.
Now with that said you can go up in the punishment tier and skip out on say Chat Restriction if your chatlog crosses the line. Usually with things like hate speech, or telling people to harm them.
Also note that you won't always get the notification that they have been punished. Someone else could have reported them and with how the system works the final person who reported them only gets the notification, let alone because of the punishment tiers if this person got just a chat restrictions they'll still be able to play. So it's impossible to know if they did get punished. But even if they didn't because you reported them (and it was a legit report) it will cause the system to basically keep an eye on them so that if anything their next legit reported incident will likely cause a punishment!