About Larry, Royce, I really don’t know. Haven’t asked him; to be frank, I’ve presumed that this particular thing on the low D you’ve mentioned was a humor thing: he’s usually clowning around when he does it. He’s been pulling off some pretty gnarly sound effects at performances lately, especially if the crowd is ripe for some good craic. If I’m not mistaken, he does cranns…next opportunity, I’ll have to scrutinize his digits with a more gimlet eye (if I don’t succumb to mesmerization first). Failing that, my ears should be able to do the job.
Still, to my knowledge, the crann isn’t necessarily a bellwether for “orthodox” trad flute playing. Depending on who’s pontificating, the flute has a very broad range of acceptable styles, some of which make more money than others. 