Upper Bar Jar shown here is very similar to Two Person Swinging Gate. There is a bystander between Nage and Uke. Nage uses the Upper Bar Jar to push the bystander out of the way so that Nage can get to Uke. Where there is no real reason to choose the Upper Bar Jar over the Swinging Gate the Swinging Gate might be better because it increases the momentum of Nage's attack. It does somewhat alter the dynamics which could be a factor.
Movie of Upper Bar Jar.
|Fig. 1 Start Upper Bar Jar||Fig. 2 Upper Bar Jar||Fig. 3 1st Strike|
|Fig. 4 2nd Strike|