I've got a Gracey with a Giraud cutter installed and had the same question about the inside and outside chamfers coming to a sharp point at the case mouth. I emailed Mr. Giraud and here is his response;
The cutter does have three surfaces, one inside 15 degree angle, one outside 45 degree angle, and a radius between the inside and outside surfaces. On your blade it should be 0.004" radius. With a standard case wall thickness of 0.012 to 0.015 on a .223 case, that leaves just a few thousandths of case for a chamfer if the radius is centered up. Add clearance to the case
fitting the case holder and the case mouth can move from a perfect fit until the inside chamfer and outside chamfer overlap. This applies to my brand of trimmer as well as the Gracey.
If you hold the case firmly, it will self center on the mating tapers of the case shoulder and reverse image inside the case holder. If you hold it loosely, it will wobble and move allowing the overlapping chamfers. This overlapping is where the "sharp edge" comes from. It is not really a sharp edge as much as a burr. If you take a scotchbrite dishwashing scrubbing pad and twist the case mouth once into the surface like you were trying to cut a circle out of the pad, it will remove 99% of the burr and leave the case
mouth very dull in comparison. You don't even have to press hard either. Some folks feel this is an easier fix than holding the case firmly and not letting it wobble.
There is a problem trying to fit each case holder to the cartridge case to prevent the wobble. There are too many slight variations in the size of resizing dies, cartridge cases, firearm chambers, etc. to make it work exactly right in all cases. If I made the case holders tighter for you, the next customer would complain his cases stick in the same holder. All in all, the size of each case holder is optimally the SAAMI spec size of the case plus 0.001 pr 0.002 for clearance. So while the "wobble" may be there, it is needed to make the fit universal for 99% of the customers.
As far as the sharp edge causing split case necks, nope, it doesn't. After 10 years and several people mentioning it, nobody has ever come back and said it did change the frequency of split case mouths. There have been comments that it could, but nobody has ever had it happen, its just a non-issue.
I can live with that.