well, i read plenty about breathing techniques and training from various angles and also practice breath exercises where hyperventilation and breath holding play key roles. i never came across anybody claiming that holding your breath especially pre-fainting (which is essential when practicing apnoe diving - and btw you seem to confuse apnoe with sleep apnea?).

to add something of substance - here is a study that does not even find any "Link between Repeated Transient Chokes and Chronic Traumatic Encephalopathy Related Effects" and that kind of asphyxiation is obviously much more extreme than holding your breath.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466005/