Actually it doesn't. With negotiations that's especially murky, because they are extremely complex and can contain proposals which don't have a chance to go into the agreement.

Explanation/Clarification is not something a voter is entitled to. He can demand it, and usually the media is giving it to him, if at all.

There is also a very good disincentives for politicians to explain "too much". Essentially, when talking to an audience of millions of people, everything you say can be used against you in a court of public opinion. Everything can and will be understood wrongly. That is also partly why effective politicians aren't particularly eager to "tell the truth".