"what societal as well as productivity improvements"
In my experience it is likely to give some sort of decrease.
I have worked in places with very flexible working hours and my team leader was always in later than me (officially we were supposed to be in by 10 am, but 11 am was more normal for him. I on the other hand got woken up by my girlfriend for her job, so i started at 9 like most other people).
Basically if I had something to ask him in those two hours I had to wait, which ended up being a bit of a pain in the arse overall.
In my experience it is likely to give some sort of decrease.
I have worked in places with very flexible working hours and my team leader was always in later than me (officially we were supposed to be in by 10 am, but 11 am was more normal for him. I on the other hand got woken up by my girlfriend for her job, so i started at 9 like most other people).
Basically if I had something to ask him in those two hours I had to wait, which ended up being a bit of a pain in the arse overall.