I'm the opposite. If my brain has to engage before 10am the day's a waste. If I "ease into the day" then once I've dealt with the world on fire stuff about 11.30 I'll power through and before I know it it's 9PM and I've been massively productive.
I think it is breaking for lunch that does it. When I didn't have any team mates in my office and I'd just eat at my desk I'd still get good work done after eating. Now I have team mates in the same office as me and we go for a "proper" lunch break - something about stopping and then having to go back to work I guess.
I learned a few years ago that defying my internal clock even has physical effects such as poor digestion and terrible stomach pain. The popular advice to rise early is harmful in my case.
In the mean time, I think, need for sleep is like appetite: some have more, some have less.
In the similar way, taking a nap doesn't mean that you sleep more, just that you schedule your sleep differently.