Not necessarily. From my perspective, it is a simple system composed of different routines. Like some people observed on this topic, players can get a lot of warnings until they even get the chat restriction. In my case, if you look at my last 2 games that led to my chat restriction, I barely said any swear word, maybe I didn't even say any at all.
What triggered the routine was the fact that I was reported by an overwhelming number of players on that particular last game (maybe the other overall small number of reports that I had from previous games was also considered in order to validate my chat restriction).
I was playing mid and started to challenge my opposite mid lane by saying on /all chat that I was going to win, that he was a loser and bla bla bla. Everything escalated and their team started to be really united by my approach. I lost my lane, got ganked by their jungle and support several times. In addition, people on my team lost their lanes, so they all had a common purpose at that point: blame me. Once the game was over I got the chat restriction right way. It is clearly an automated system.
I think it is fair, because what is the odds of someone being reported by almost everyone else on that match. This simple trigger makes everything relatively fair. Questionable, but fair. There is no artificial intelligence or anything more elaborated taking place on the chat restriction routine. It is probably just a rudimentary workflow that check your standing and the number of reports. Very basic and cheap, but interesting.
If I had to improve something, I would remove some hard coded phrases that just increase maintenance cost (and subjugate the reader's intelligence) and I would include the complete chat transcript (not just what the restricted person said) so they would have a chance to understand in context what they did.
So long story short, I don't think excessive swearing is a major factor, but perception is reality, sooo, if those other 9 people feel like you are being disrespectful, you will get the restriction even if you didn't use any bad words. Bad behavior will get caught - Yes for sure. Some outliars and minorities that should have their view protected will be caught as well - Yes for sure.