Ahh now I understand what you mean. Like to fill any crevices I’m the unevenness of the shape of the inside of the outer tire.
I thought you meant like when the tires spins fast then it spreads the slime evenly around the tube which makes the average density around the tire more uniform and to that I’d say it wouldn’t really make a difference unless the slime is very heavy (a decent fraction of the tire weight) to help average out weight imbalance in the tire.