It’s possible that Hogwarts is protected against portkeys in, but not portkeys out. We saw that sort of 1-way wards was possible in Azkaban, and it might be smart to leave a method of getting out that could be used to evacuate somebody/everybody on short notice.
It’s possible that Hogwarts is protected against portkeys in, but not portkeys out. We saw that sort of 1-way wards was possible in Azkaban, and it might be smart to leave a method of getting out that could be used to evacuate somebody/everybody on short notice.