It doesn’t, as far as I can tell. The holes are so small and smooth(on my chanter anyway) they can barely be felt, especially felt enough to know how much you’re covering. It also sounds weirder on a chanter than on a flute, and you can’t just half-hole, you have to vent something sometimes too. I’ve played flute a bit longer than pipes(actually I’ve played pipes slightly longer than the wooden flute. I’d forgotten that), but even taking that into account, I find half-holing flutes to be a lot easier than pipes. Oh, and half-holing with pipers grip also feels awkward. Maybe that’s just me, I don’t know.
Smaller holes means the tolerance for exact finger placement is much smaller. In general all that is required is a slight “leak” of a tonehole finger.
One technique that works for many people is quite different from what you’d do for half-holing on a flute; rather than lifting the finger, or rolling it up or down, you curl the finger around the chanter and pull with the far joint of the finger. This tends to cause the seal between your finger and tonehole to leak on the opposite side, in other words the side nearest your wrist.
Ooo, let’s wave the big names about! No, he is not wrong, but he is an exceptional player, rather than the rule. For mere mortals such as myself, half-holing at speed on a UP chanter is more of a gamble than a bona fide playing technique.