First of all, a 15-day waiting period is problematic. Why not 13 or 18 days? For a patient who is very close to death, this makes no sense.
Secondly, the vast majority if not all patients with a terminal illness have had plenty of time to think about their problem. It is not a decision that is made in 15 days.
A 15-day waiting period can be problematic, for instance, if the patient is suffering a great deal, is competent and gives consent to receive medical assistance in dying. If a well-intentioned physician then administers barbiturates or morphine to the patient to relieve pain, the patient might no longer be competent to give consent when the physician visits again, owing to the high doses of narcotics.
To my mind, this is problematic.