Slitherine

Quick question/thought on the diplomacy - I noticed when I raise my level of agreement, it resets the prior agreement to zero. Example I get a Non aggression agreement, and after five turns it caps at +5 - I then in my opinion show more diplomacy in a Mutual defense pact - instead of upping the diplomacy number i get +1 next turn on its way to (+10) for the mutual defense, and an immediate -5 for my loss of the Non Aggression pact. One would think I would keep the non aggression pact, as it is part of the mutual defense (5) and then maybe only add (5) more for the next 5 turns of Mutual Defense, vice start back to zero? And so on with Alliance? Just my two cents. Salute