How can label smoothing affect knowledge distillation?

A teacher network is trained using substantial label smoothing and is later used for knowledge distillation. Which effect is most consistent with published findings?

Label smoothing changes only optimization speed and cannot affect the information transferred to the student

Distillation necessarily improves because smoothed targets always produce richer dark knowledge

The teacher's top-1 accuracy must decline, making distillation impossible

Distillation may become less effective because the teacher logits retain less information about inter-class similarities