Is the Rambam quoting from the Talmud?!

I found in the Rambam's responsa that he wrote that he changed from the Talmud:
"Our question and our Torah have excluded what you mentioned in the law, 10:1, 20, lest he err between God and him, and the language of the laws, lest he err between God and this, the true text will explain to us:

Answer: What is mentioned in the laws, lest he err between the Lord and the Son, is correct and is the language of the student, as is what the Lord says there. And I remembered the thing that is found in the majority, and it is a mistake, one hour after another, and you did it as if the wonder were less, that our intention in all this is to bring the laws closer to reason or to the matter that is closer (* copied from the act of the cook:): Moshe ben Rabbi Maimon, zt"l

And I was very surprised by that. Are there other examples of this? Is it legitimate? Did other rishonim of the Talmud do this? What is the explanation for this?