I think the difference in what you were taught and what we were taught, @Mimishu1995, is that this is such a fundamental part of our language (as fundamental, for example, as “what letters sound like”), that it’s just not taught to us formally. When we grow up with it then we know what sounds right and what doesn’t, without even putting it into a formal “rule” like that.
I’ve been speaking English for more than 60 years, and writing it for not many years less than that, and I only last month saw this listed as “a rule of English” for the first time – ever. It makes perfect sense to me, and I like the instruction to “try to violate it if you want to sound like a psycho” – or an ESL student, I suppose – because it’s sort of true. On the other hand, I’m sure that there are many perfectly valid violations of that “rule”, too, by perfectly good speakers and writers of English. But you sort of have to know the rule to be able to violate it in a knowledgeable way, too.
It’s the kind of important, universal, old, syntactical rule that you really can’t violate with impunity. Not the kind of old, syntactical, universal, important rule that you would violate just any old time.