This goes back to Marx's Capital, where he talks about how Capitalists want to push for night work/24-7 operations because machines don't make money if they are idle.
Flex hours is really just a way to make you work 24/7 because that's the nature of "knowledge" work - it's large periods of downtime with sporadic big outputs. The point of answering emails at all hours of the day is eliminating the slack inherent in the process and pushing things through as quickly as possible, just in terms of white collar work vs literally making widgets in a factory.
This goes back to Marx's Capital, where he talks about how Capitalists want to push for night work/24-7 operations because machines don't make money if they are idle.
Flex hours is really just a way to make you work 24/7 because that's the nature of "knowledge" work - it's large periods of downtime with sporadic big outputs. The point of answering emails at all hours of the day is eliminating the slack inherent in the process and pushing things through as quickly as possible, just in terms of white collar work vs literally making widgets in a factory.