From what I've seen all of those deaths are from people ignoring his repeated warnings and advice in all of his materials. I do think some of those warnings were added after people died, but they are still doing things he has never done himself or told people to do.

No part of his method suggests hyperventilating or holding your breath immediately before, or while in the water- it is something done separately or beforehand, and he explicitly tells people not to do it.

I am also a freediver, and it is well known that hyperventilating before holding your breath is a deadly thing to do in the water, because it can cause blackout- and that seems to be what people are (incorrectly) doing here.