"150 Driver. Did you really solo without knowing about carb heat? Did you solo without passing written exams? "
No on both counts. But I didn't solo after 8 hours either, more like 20. By the time I'd solo'd of course I was using carb heat (and flaps etc), but even then, I question whether I understood what everything did, I think I was probably still flying by rote.
As to exams my Instructor insisted that I'd passed Air Law (now two papers ?) before going solo.
For me it was an issue of 'Monkey see, Monkey do', but then Monkey studied and eventually Monkey understood.