While that is true, and the full context only makes it worse, the important reminder is that a lot of people have died doing "Wim Hof" breathing before diving. It is not safe to hyperventilate before going into the water, because you are not saturating your blood with any more oxygen (normal breathing accomplishes that), but you are rejecting CO2. Your urgent need to breath is not triggered by low O2 but by high CO2.

So if you hyperventilate and then go under water, you will experience an urgent need to breath after you start to become hypoxic. This has killed people and will kill again. Don't let it be you.

https://en.wikipedia.org/wiki/Freediving_blackout#Shallow_wa...