Honestly, I don't much care about which translation or how it was mistranslated or anything like that; things were added and taken away and edited and all that lot all through its history, such that the book we have today is likely entirely different to the book that was "originally" put together by the very first "Council...." I just work on the book that is presented by most Christians today as the basis of their faith, and in that
version - the one shared by most of the Christians on Earth - there are two sets. I honestly don't know when the second set was slotted into the bible or if it was there from the beginning, all I know is that it's there in the commonly accepted versions of the bible today, and that's the one I'm going to look at when talking with a Christian. In this case, I'm not overly interested in the prose or the translations or anything; I'm primarily focusing on what happened narratively.
But a slight note on the translations: The original text - even if what you're saying is correct - in this context doesn't matter.
The current versions that most if not all Christians use has that distinction of the two sets being made, and so that's what should be used to discuss the current faith. No point in dragging up an earlier version that doesn't match the current version if the Christians are using the current version as the basis of their faith, y'know? Especially since the Septuagint isn't actually considered part of the main Christian Canon; the Catholics use a lot of those books, but their own versions of them, and the Protestant church rejects most of them as non-canonical. So talking about the Septuagint when talking about Christianity is pointless, since everything that is considered "Canon" is in the current bible, and a lot of things in the Septuagint are rejected as non-canon. I think that the "extra" works are classified under the Apocryhpa, which are the "hidden" or "extended universe" books, as it were.
Interesting in and of itself and something I'll be looking into in more depth than just my current basic google search, but ultimately irrelevant when discussing theological concerns of modern Christians since the Septuagint is normally never accepted as Canon in its entirety and usually just added on as an extra little footnote.
I mean, if you want to get technical, I don't accept the existence of either
of the sets of Commandments, since I don't think Moses ever actually existed as a person.
But again, that's a debate I would really rather not have today, haha.
As it is, I think we're slightly derailing the topic of this thread, so perhaps we should dial it back a little.