As far as I know, Julia Kristeva coined the word "intertextuality" (in
*Revolution in Poetic Language*) and she explicitly does *not* use it to
mean "historical influence."  So the relevance of historical "closeness" may
be moot.  Of course, many others have used the word since Kristeva to mean
all sorts of things.
For those who will be there, the SBL Semiotics & Exegesis Section will kick
this topic around a bit in San Francisco.  (Now there's a gang who don't
believe that author's intent determines meaning!)
George Aichele
(just one of the gang)