Yes and no. You can understand a concept 100% and execute it 99% and still have the program fail. In other engineering disciplines, that gets you a good grade. In CS classes it's a fail.
So you have to sit there and make sure it actually works. I'm not a programmer, but I took CS courses. Debugging your homework is fucking awful. I understand it's a skill necessary for programming, but it's awful. Especially when the bug is a mistake that is unrelated to the topic of the homework.
I remember pulling an all nighter trying to figure out why my problem set didn't diff correctly. I must have spent 20 hours on a single bug.
Isn't that what makes CS easier? You get immediate feedback. You know if it will be right or wrong before you even turn it in.