Are they actually productive for 72 hours per week (9am-9pm 6 days per week) though? At some point wouldn't the burnout make them only as productive as someone

Are they actually productive for 72 hours per week (9am-9pm 6 days per week) though? At some point wouldn't the burnout make them only as productive as someone working maybe 50 hours per week but with time to learn and relax? But also, if 996 includes things like studying to become a better programmer, taking breaks to get coffee, etc. then maybe a lot of us on HN are working 996, if we include our own time we spend learning.