Yes. If you try to hold your breath, the pain you feel is from CO2 buildup, not because of a lack of oxygen. If you lie still, the oxygen would last for many many minutes, but most people will be in such a pain after a minute or two that the body refuse to keep holding the breath.
Consequently, that's why hyperventilating is absolutely a no-go when freediving. It tricks your body, by not triggering the CO2 feeling. So then you can suddenly pass out without feeling you were close to running out of air.
Is, at the same time, hyperventilating an effective (but very dangerous) way for people to get better at freediving? It seems like it would help people get deeper, especially when they are no where near their limits. That also sounds like it would make things even more dangerous, because when you get better and do get near your limits, you don't notice.
For most people, I think the increased heart-rate of doing the big breathing motions would nullify the theoretical gain. So it feels easier, but you can't really hold any longer, you just pass out unexpectedly.
The best way to get better is to do "co2 tables", just slouch in your couch and do the intervals of breathing/holding, and learn to control your body. When actually diving, we never push our limits, compared to what we know we can handle on land. Like, I can hold my breath for 5 minutes, but would seldom be more than a minute underwater.
Co2 tables are actually very meditative. After the first convulsions, if you manage to calm your body down, it's quite a weird headspace to be in for the next minutes.
Consequently, that's why hyperventilating is absolutely a no-go when freediving. It tricks your body, by not triggering the CO2 feeling. So then you can suddenly pass out without feeling you were close to running out of air.