I had the opposite experience a few years ago, I am very much a night owl.

I did a job that required me in the office for 7am for a few months, I was noticeably less effective for the whole duration, I was just slower at everything and was basically constantly tired. Switched back to getting in for 9-10am and the difference was night and day, as basically I was back to my old levels of effectiveness after a day or two.

I just think I'm one of these people that cannot adapt, or at least if I do, it comes with a cost.