Stress is greater in tack fused pieces than in full fused. Tack fused pieces to some greater or lesser extent behave independently from the base and surrounding pieces. This means that more care must be taken in the anneal cooling of the glass.
Stress is dissipated more evenly in rounded tack fused pieces so the stress is not concentrated as individual points around the edge of the glass.
Stress is however, concentrated in corners of rectangles and in points of triangular and the ends of thin pieces.
By nipping the corners off these sharp angled pieces, the amount of stress concentrated there can be reduced. Very little needs to be removed to have the effect. So the appearance of the angles is hardly affected.
Using your grozing pliers, you can take a small piece of the corner off. It needs not be much more than a large grain of sand. This should be done at all corners and points. It will not reduce the amount of annealing or the rate of cooling, but will assist in reducing the possible stress built up in the tack fused piece.