I agree with your basic point, but if you mean to say that some other set of exams (the non-general ones) were harder, I'm not so sure. For most places, there are two sets of exams: generals before you write a thesis and your thesis defense. In my experience, pre-dissertation general exams are significantly harder than the oral defense of a thesis. Most universities use them as a final weed-out phase before allowing people to even consider a thesis topic. As such, you have to demonstrate mastery over a far wider field than a dissertation might cover. For example, all of Math or Philosophy or English Literature or Romance Linguistics - often with chosen specialty sub-topics, so you end up having to worry about breadth and depth. By the time you get to the oral for your thesis, on the other hand, you are in such complete command of the material that defending your views (on that narrower scope) is relatively easy.
Also, in most cases, you won't be allowed to set a date for your dissertation defense unless the work as a whole is already passable.
Definitely my experience. I still have vivid nightmares about the general exam more than 10 years later. It was an 3 day x 8 hours per day written test with no breaks. If you wanted to eat, you had to bring food with you into the test room. Then there was the dreaded oral inquisition. Although I didn't appreciate it at the time, having survived the abject misery of the first 2 years of a physics Ph.D., everything else has seemed manageable in comparison. A few years ago, they changed the format of the written exam to a single 8 hour day. My thesis defense was a total cakewalk. Scheduling it late on a Friday afternoon was probably the single smartest thing I ever did in grad school.
I agree with your basic point, but if you mean to say that some other set of exams (the non-general ones) were harder, I'm not so sure. For most places, there are two sets of exams: generals before you write a thesis and your thesis defense. In my experience, pre-dissertation general exams are significantly harder than the oral defense of a thesis. Most universities use them as a final weed-out phase before allowing people to even consider a thesis topic. As such, you have to demonstrate mastery over a far wider field than a dissertation might cover. For example, all of Math or Philosophy or English Literature or Romance Linguistics - often with chosen specialty sub-topics, so you end up having to worry about breadth and depth. By the time you get to the oral for your thesis, on the other hand, you are in such complete command of the material that defending your views (on that narrower scope) is relatively easy.
Also, in most cases, you won't be allowed to set a date for your dissertation defense unless the work as a whole is already passable.