J2EE is an extension of java i.e. Core Java does not include all J2EE aspects.
While a person working with JSP and servlets ideally should be well-conversed with core java because the language is java, it may not be necessarily true. Quite a lot of routine servlet maintenance may be done even with a light knowledge of java constructs if the coder has programmed in some other OOP language.
Also JSP+servlets are a miniscule part of j2ee
So even if a persons knows this, it can't be guaranteed he/she knows j2ee per se.