I haven't met a good professional programmer working in webdev who didn't know their way around linux.
I've met plenty of bad programers who got into this field for money, didn't know how their way around unix, were barely able to do fizz buzz and would be better doing something else. I haven't hired them though. Not knowing one's way around linux is a sign of lack of curiosity and passion for the topic.
It's obviously different in some fields (like gamedev) where the code produced by the dev is not supposed to run in a linux environment.
