I do not know of an "official" position on this, but in talking with some of my colleagues would say that the initial supposition that it is just how the glass formed on the dicor is correct. This "spiraling" should not cause any defects in your output.
The fact that one of the dicors had this spiraling on it when the magenta artifact occurred for yuou Bryan could have been coincidence. Defects due to a bad dicor are usually because of a crack in the glass and, while possible, it is unlikely that this was because of any spiraling that you noticed.
