I've not heard this version. I have heard reports of other people using the stairwell located by room 135. Some of these were supposedly dressed as security personnel. Those windows I believe would be to exposed for escape.
My opinion is there is more than one shooter and from the lack of gun flashes from the 32nd floor location on any videos this may not be the primary shooters location? The guns observed in the room video have standard flash suppressors which wouldn't mask barrel flashes fired from these windows on target. So where are the barrel flashes? Now the flashes could be masked shooting out the windows from deep inside the room. But this shooting wouldn't have been on target for the concert. We know there were shots fired on the fuel storage area at the airport. Maybe these shots weren't targeting these tanks. Maybe they were just shooting out the windows of the 32nd floor from deep in the room as a disguise so the police would target this floor? There are a lot of questions which are unanswered right now.
I provided video in another post in this thread with witness Brianna stating they were warned to leave the concert or be killed. This is a really important lead to follow up on.