I agree with you 100%. For web programming, I'd say it is understanding the http protocol. Many people can code in asp.net or even write servlets but don't know how session work, cookies or basic things like the differences between GET and POST.
Also keep in mind that there is a industry full of recruiters who don't agree! If the job ad says you need previous experience with Boongolatr.js version 3.147 then Boongolatr.js version 3.147 it is. Then good fundamentals and knowing Scheme, Haskell and shit won't help you.
Some people seem to think the difference between POST and GET is that POST "doesn't show the parameters". That's wrong. POST has a body, and GET does not. The "parameters" go into the body of the message (after the header and \r\n\r\n)
Also keep in mind that there is a industry full of recruiters who don't agree! If the job ad says you need previous experience with Boongolatr.js version 3.147 then Boongolatr.js version 3.147 it is. Then good fundamentals and knowing Scheme, Haskell and shit won't help you.