I don't think you should COMPLETELY disagree with Adrita's statement because some markers do base the writers skill on the introduction. It's like when you're given a first impression about something/someone and assume that it's consistent throughout it/them.I completely disagree with Adrita's allegation, just letting you know. I wouldn't be so quick for taking that "advice" on board.
But yeah an introduction to an essay is like an introduction in a narrative, you have to keep the reader (or in this case the marker) engaged