We do have relatively reliable Bibles with regard to one another. There are clearly noted additions in some places, some more generally noted than others. There is still more to an iceberg than what is in view. So there can be other bits of text not originally in scriptures.
Jeremiah 8:8-9
"How do you say, 'We are wise, and Yahweh’s law is with us'? But, behold, the false pen of the scribes has made that a lie. The wise men are disappointed. They are dismayed and trapped."
Yes, allowances and permissions are gracious accomodations. They are different, notice that difference, from how it was in the beginning, it was then in God's design, and God's will is perfect. It doesn't change.
The new covenant is based on the old covenant, that was needed, and the new covenant is the fulfillment, with Christ being who we have for the priesthood, the needed effective sacrifice for atonement, and the way to be clean. It does not contradict the old covenant, which was with shadows of what was to be shown in the new testament. Nothing did away with commandments, while Christ was the only one doing everything according to it, to be the perfect one, which was fulfilling that. God's will is still shown, as always, first, where there is anything in contrast to that.
The new covenant was promised to those people of Israel, the law in their heart would not be with anything different to the commandments they were shown.