Yup. Used to hear that explanation about how the rounds were put together every time weapons platoon talked about 'em. Since it was always pretty nearly a word for word match on the description, I'm sure the spotting round's construction was covered as part of the SMAW gunner's training syllabus. The base of the round certainly has a "different" look with that bullseye arrangement of smaller diameter cartridge head inset into larger cartridge head. Looking down into a fired case, the Hornet blank's mouth is usually pretty well flaired out down there below the 7.62 NATO case' shoulder. I have my doubts that it'll ever catch on with reloaders.
Got to fire a partial magazine of 'em and light off a simulator for the rocket a time or two during cross training. The weapon has a nifty arrangement where the scope has stadia lines that make it relatively easy to read the impact of the spotter round and translate into the same amount of holdoff to correct the miss, combined with a thumblever that handles switching from spotter to boomer with minimal effect on disturbing the hold.