No, I didn’t consider it. The main obstacle is the cost of conversions, as you said. Besides, it’s not always possible just to remove extra triangles
The top triangle can be very narrow, but it’s impossible to easily fix the situation. In fact, we have to split the top edge and re-tessellate it, which is too expensive.
There can be adjacent polygon above this shape and we have to consider it too, splitting it synchronously.