The simple answer is "yes".

IMR stands for "Improved Military Rifle" as that was the intended use for single base nitrocelluose gunpowders. The various burning rates are achieved by granule diameter, length, single or multiple perforations, and deterrent coatings to control burning rate by determining surface area and "ignitability".

A couple of them use finely cut flakes, but they also started as extruded powders. These faster powders were developed for shotgun use. IMR 4756 comes to mind.

This is one of the interesting areas of smokeless powder development. The europeans developed small arms propellants by going to rolled sheet-type powders and relying on chopping up the granules into regular shapes. American propellants started off as extruded rod shapes with perforations, and then chopped up into lengths to control burning rate.

Both methods rely on granuale size to control burning rate. My guess is that the American extrusion method was copied from the traditional British method of making Cordite. With the proliferation of small arms ammo making technology, both methods are used worldwide.