No, You Don't Have To Cut The Upper Rail
In my University of Extrication skills training, the question always comes up "I took a class and the instructor said you have to cut the Upper Rail before you roll or jack the dash". In my opinion and based on my experiences, No you do not necessarily HAVE TO cut the Upper Rail.
It seems that it always works better in training when we make that relief cut before we jack or roll the dash. Reality however is that we are working on 'virgin' cars in our training that have not been in a frontal crash like what would really happen with enough force to trap a person in the front seat.
This 1997 Honda Accord required the jammed driver's front door to be opened and cut off at the hinges. Dash rolling or dash jacking was not necessary to remove this patient.
Look at the Upper Rail. Look at how it is already crumpled, bent, crushed, and 'hinged' by the crash. That's the Real World!
My reply when this question comes up in training is that cutting the Upper Rail is always a NICE TO DO but most likely will not be a MUST DO when you are moving the dash to free a patient.
You DO HAVE TO cut the A-pillar to disconnect the roof from the lower A-pillar. I recommend cutting a chunk out of the pillar so the stubs pass by each other without binding up as the dash moves.