70 hr for 6 working days averages to 11+ hr per day. Add another 2-3 hr for transport. Unmarried may be able to spend that much time, but married persons with children can't. If 70 hr a week is implemented, soon, there can be resignations. In present day life, both husband and wife have to work to meet children education, own a house and have money for post retired life.
Again as children grow up, health of own and taking care of aged parents will need time for the family.
Work from home wherever possible may allow for personnel to work extra hours. But, not true for all organizations.
Already, we have growing number family court cases. More hours of work along with travel time will add to family quarrels due to work stress, uncared children and chaos in the society depending upon how the children will shape up. To address this, organisations should be able to provide facilities for creche, schools, medical facilities for family, either by individual organization or by joining hands with others.
Even then, allocating 13-14 hr a day will disturb family life. In the long run, it will have negative impact on everyone.
Extra hours for national growth can be added by increased automation, use of machines and tools where possible.
Nation's growth can be achieved by wise spending of the revenue. Money spent should add to growth of assets, not for paying day-to-day living.
https://www.moneycontrol.com/news/trends/bengaluru-cardiologist-on-narayana-murthys-70-hour-work-week-advice-wonder-why-young-people-are-getting-heart-attacks-11616091.html