I assume they're talking about the fact that basically everyone that learns Rust goes through a period of "fighting the borrow checker". Part of the way that rust ensures memory safety is by preventing you from doing things that it can't prove are safe to do. For people coming from languages like C or C++ they've been able to get away with doing things that are probably unsafe but that work either through luck or very careful planning. But since the borrow checker can't prove that some of these tricks are safe it will just say "no" and fail to compile.

Within a couple weeks you will get the hang of what the borrow checker can actually handle and you'll mostly not have problems except when you are actually making a genuine mistake.