Paul,
Those bullets are sized to .454 primarily with the intention that they will be fired in Colt SAA's and their various clones. These guns very typically have cylinder throats that are from .455"-.457" in diameter while groove diameters of barrels vary from .4505"-.453" depending upon manufacturer and the dates of manufacture.
Some of the earlier Ruger Blackhawks in .45LC also had large throats measuring .454-.455" diameter as well.
When increasing the bullet diameter to more closely match the true diameter of the cylinder throats, accuracy increases and performance is more predictable.
Now, to answer your question regarding the .454 Casull. If attempting to use these .454" diameter bullets in a Freedom Arms .454, the loaded ammo probably won't even chamber due to the tight tolerances of the FA guns.
In the Ruger, and the Taurus it is questionable that they would chamber in these guns either. If they did, they would probably lead the bore, as they are too large for the cylinder throat dimensions, and the forcing cone area would soon become leaded heavily.
They would pose no hazard from a safety standpoint however, if they would chamber, these guns wouldn't even know the oversize bullet was there in regard to pressure.
Hope this helps answer some of your questions.
God Bless,
Marshall