This was a lot more common "back in the day" to keep position sensitive powders that did not fully fill the case tight against the primers to insure consistent ignition.
It was considered by some to be even more important further back with black powder. The contention was that, since BP burns faster than smokeless, an air gap could lead to an unsafe pressure spike and "ring the chamber". This was a point of argument in the 19th century. Gun debates are nothing new.
Cream of Wheat was a very common filler as it is similar in consistency to the powder. Also the dacron quilt material the OP mentioned.
It's far less common today and usually considered unnecessary. I load .45 ACP with 4.3 grains of Titegroup. That takes up so little space in the case that I could triple charge if I wasn't careful. I've never had a problem with ignition.