My opinion has always been a analog IC system engineer is the one who creates a product family by knowing what customers want, creating all the specs and architecture completely from scratch. Like predicting the future of the product evolution. I would then say an analog IC designer would just make a product that a he/she is told to make... I am not saying that the analog designer doesn't invent things... Its just a lower level designer. Like think on how you first started out doing IC design. You didn't just start out say... I am going to make this new power block with blah blah blah.. Someone told you to make it... the system engineer guy/gal..
Just my two cents,
JGK