Meh, my last company/team had work hours that were almost completely flexible. My team had one weekly 10 o clock meeting that I had trouble making consistently (I had a longer commute than most), and we moved it.
It's honestly not _that_ universally difficult, because in practice "completely flexible work hours" means that there will be a good few mid-day/afternoon hours during which everyone is around, and lumping the meetings into that time works perfectly well. Obviously the extreme case as described in this article would make it more difficult, but for most people I don't see why it wouldn't work and even the extreme case people would be somewhat better off.