I thought one generally doesn't include lunch in the day length. So an 8 hour 'day' with an hour lunch is 8-5, 8 hours working + 1 hour off-time.
When they say "6 hours" in this article, they're excluding lunch.
Interestingly, while lunch isn't counted towards the 8h, the workday normally does allow for coffee breaks ("fika") on paid time totaling 15-60minutes depending on what business.
That's up there with "You can't work remotely but we expect you to VPN in after hours to fix any issues".
Break-fix work needing to be done on-call/24x7 while requiring in-office presence for design and new feature development (a fundamentally different type of work, typically requiring a higher level of collaboration) seems perfectly reasonable to me.
I live in a northern climate and when it snows can either spend 1 hour stuck in traffic or just work from home (and possibly come in after traffic has cleared).
My previous employer was adamant about being in the building from 0830 to 1700 even if it was a blizzard. My current employer lets the employees manage whether they need to come in or not (any day not just during bad weather). I'm sure you can guess which one has happier and more productive employees!
The key there is (almost) no one will be in the office because it's a synchronized event. OTOH, if everyone worked from home 2x/week at random, it would be chaos trying to plan whiteboard design sessions.
If you have any kind of agreement on "unpaid OT" you typically have 1 more (so 6 or 7).
Being on call would mean I'd want ar least another one or two.
So in reality the standard work day is 8-12 plus 13-17 so 8h work in 9h total.