Maybe I'm wrong (not a doctor), but I believe it is very unlikely that one off events of apnea lower your saturation to a level of clinical relevance to need 2s frequency; saturation drops only after a continued chain of such events or some sort of constant obstruction (COPD, asthma exacerbation, etc).

Also, though sample of n = 1, training for freediving my breath holding PR is 3m31s, and my SpO2 barely went down. The CO2 reflex kicks in before O2 goes significantly low.