As far as I know the Minsk accords were drafted in 2004 way after the Two by Four agreement I think you are referencing.
In the Two by Four agreement some officials in negations had made assurances. These assurances never made it on the official treaty. Even if they were actually said at all which there is debate. Personally I do believe they were said, but what makes it into the official document signed by everyone is what you abide by.
If someone told me they would do something personally, but then the company they were with handed me a sheet that did not have the assurance on it. I would be asking for it. It's not like this is something that could have just slipped by. The treaty is actually short enough to be read by anyone, and I doubt the entire Russian government was stupid enough to let that one through if they really thought it was the case. What is said in negotiations to the treaty is always all over the place while the whole thing is getting hammered out.
Unless you mean some other treaty?