I'd say although the number who get full marks obviously isn't that high, it's still significant and by no means anywhere near impossible for exam 1. Exam 1 is designed so you have plenty of time, and it typically isn't that hard and won't have any questions where you literally have no idea what to do (as is the case in exam 2). Given that, as long as you know the theory and you're careful it's quite possible. As for:
wouldn't the examiner mark you some small errors "on purpose" in order to prevent a full mark? most of the teachers in my country are...........
Then just don't give them any chance to even take marks off. Simple. SM will never have what happened to methods two years ago anyway where they began deducting marks for stupid things because too many people got full marks.