The rules are open to interpretation by the administrators. If they were set in stone and interpreted literally people would find ways to "game the system" and abuse it in different ways. We don't want that.
Secondly, my personal feeling is that negative feedback is a dangerous tool. If people leave it too easy, it encourages more discussion, the party receiving it will want to contest it or leave retaliatory negative feedback, and so forth, generally pushing things into negativity, fighting and endless defensive arguing.
We would rather prefer to encourage people to discuss things in friendly ways in private, and agree on solutions to tricky situations (like in this case, a possible delayed shipping). Trying to propose another trade in a friendly way is the solution to that, not instant negative feedback.