Its difficult to get a good crimpif you don't have a groove or cannelure to crimp into.
Solids are not compressible.
To confuse the issue,jacketed handgun bullets may well have a knurled cannelure.Lets set that aside for a bit.
Military type jacketed rifle bullets often have a cannelure exactly where the military would want the bullets crimped.It will be a taper formof crimp,rather than a roll crimp (ideally) In a repeater rifle,like an AR,the concern is bullet setback,into the case. Not so in a revolver.
Especially in a beast like the .454,you need a ROLL crimp to resist the bullet coming OUT of the case,for at least two good reasons. The cylinder throat is a slip fit to the bullet,or you could not load the wheel easily. Then you have the cylinder gap,which leaks.Then the forcing cone. Untill you hit rifling,there is not enough resistance for good ignition,especially with slow Magnum type powders.
A good crimp will hold the bullet till you get fire in the hole.
The other very good reason is recoil pulling your bullets. Yes,neck tension helps,but your 454 Casull needs a good crimp into the molded crimp groove.
Crimping as a separate step takes another stroke,butit is WAY easier to control.
If you have a crimped factory load in 454 or 44 mag,look at it close for a model.
A tip: Max 454 loads hit 60,000 psi. You need to have a cartridge or brass in every chamber of the cylinder or gas blasting back through an empty chamber can get hard on theloading gate of a Freedom Arms single action.
You may notice a crimp ring around a cartridge at the base of a bullet.That resists setback in,for example,a lever action,both feeding and stacked in a tube mag ,while the roll crimp resists bullet pull and aids ignition