To my knowledge, this is pretty standard advice among students - review your notes before you sleep to help you remember them.
The explanation I've heard is that sleep is when long-term memories are formed; something put into short-term memory will have less time to erode if you sleep right afterwards.
I have heard a similar advice, but in the morning before class. Your brain has the most capacity in the morning, because over the day all the other information makes you exhausted and the amount you can learn on a single day is limited.
It is way easier to learn in the evening, that is what most students do anyway.
The explanation I've heard is that sleep is when long-term memories are formed; something put into short-term memory will have less time to erode if you sleep right afterwards.