He did this to physically shield himself from random shrapnel. His purpose in opening the balcony door was to give the impression that somebody may have egressed.

This is taught in tradecraft courses, and this mention along with others in the article suggests to me that he's been through some tradecraft and/or SERE-type trainings -- probably oriented towards journalists.

Or could be perceived as a diversion to allow the person enough time to get down their makeshift rope.