Sometimes, (Just my opinion/take now) when someone gets too close to any paticular cigars last third, it gets too hot. Meaning that the cigars burn gets too hot, to where the temp feels too hot on your lips, and taste buds. This definitely affects the flavor that you experience as well.
Have you ever noticed that if you go too long between draws, and that you try too hard and fast, to draw to strengthen a weak burn. That the taste is unpleasent? This is usually because the smoke that you are getting is too hot after drawing on it too quickly.
Kind of hard to explain other than that. Maybe someone else can do better than I did at describing the term hot.