I had forgotten about this untill I was messing with my car a little bit ago. It helps to keep the seal in its original shape and to help support it.
We do this at work occasionally if we are having trouble getting new seals to seal. We run a vacuum hose usually along the lines of a 9/32 size, we peel the seal off of the hatch, run this hose through it and then reseal it to the hatch, I've done it on the car as well but it is harder to do because of the curves and where there are already impressions on the seal.
Just something I remembered and thought it might be helpful.