This sounds a lot like the discussion on "pressing"; is it "restoration".
Let me first say that I have never clean and/or pressed a book.
With that being said, I tend to think that if nothing is added to the book (pieces, color touch, ink, glue, etc), it is not restoration.
I occasionally wash my 57 Chevy and I don't think of myself as "restoring it". (maybe this is a bad example).
Of course that definition is not perfect as some could say that "trimming" does not "add" to a book, but is restoration.
I think, however, that if a chemical is added to the book to clean it, that it should be disclosed (thus I like the fact that CGC does leave that on the label).