Usually this gif is shown without the comparison video, and there is another one too. The poster usually says this was the real video that got leaked, and the versions with the planes have been edited. I believe is a dis-info campaign, to discredit those who question the impossible physics of the planes, and re-enforce the now thoroughly debunked and discredited idea from September Clues that all the videos with planes have been edited.

There is also a similar misinfo gif of charges exploding in WTC7 - again, edited in and portrayed as rare leaked footage.