There's a difference between the airport being closed and the airport terminal building being in "hibernation" for 2 to 6 months. Note the line in the letter which reads “In the interim, operations of medical, relief, cargo flights, or other, will be possible from the FBO building.” The FBO was used after Irma, and before the tents were installed. If SXM chooses to allow passenger flights, and if airlines choose to operate them, they can be handled through the FBO.

Personally, I'm in no hurry to go anywhere farther than my local grocery store.