Haha wow very similar. There's a guy here in a neighboring team that I used to work under that literally just falls asleep at his desk and snores. Comes in at 9:20, leaves at 3 some days.
Which general domain or area are you working in?
Is this your first job?
I also have some imposter syndrome about being a "real" dev. I think that's because there's so many ways to go from here. Whereas, for example, if you were a doctor you would basically lock in your area of practice and then put your head down and get it done. For us, you could: build your own product, climb corporate ladder at BigCorp, startup world, freelance, freelance while traveling, consult, be a product manager instead, etc.
The cushy part is tough to give up, but the free hours don't really make up for the existential dilemma that eats at my soul every day... I know right, first world problems.