If they say 8 hours (full work day), they're either lying or using some kind of performance enhancing drug.
I've been paid for software development for close to 20 years and I've never done anything productive before lunch. Mornings are for documentation, code reviews, emails, stuff that doesn't really need constant focus. Afternoon and early evening are when I get shit done, that's when I can get into the Zone.
The point was that being "productive" - that is to say fully focused - for a complete workday just doesn't happen all the time without medication of some sort.