He's saying that it's a great way to command a high salary, but that it also closes some doors to you if you want to maintain that salary. It's not advice to "

He's saying that it's a great way to command a high salary, but that it also closes some doors to you if you want to maintain that salary. It's not advice to "go for it" or "stay away from it". Rather, it's pointing out a tradeoff that isn't obvious to a lot of early career folks.