Lesson: A Grunfeld theme

http://www.chess.com/chessmentor/view_lesson?id=5818

Hi all, i am new to the forum so i am not 100% sure this is where i should be posting this, anyway...

Can someone please explain this lesson to me for i am utterly lost... The move Ne7 seemed obvious to me; it stops Ne4 and prepares for moves like Rac8 and Bf8. However according to the lesson the best move is f5. I just cant see how f5 could be considered a good move here. It totally exposes the king after exf6 and creates an extremely weak e pawn for black. Furthermore, i ran the position through Fritz and Fruit 2.1 and they both agree that Ne7 is the best move. What am i missing here?

edit: Fritz and Fruit 2.1 both agree with Ne7.

If you don't understand it, you're probably playing the wrong opening.

? Its a lesson, a single move lesson...

"relevant and helpful"

simply, i was wondering if what others thought of f5 for in my mind it is a far worse move than Ne7.

Its not that i care what the engine says. I ran it through the engine, after completing the lesson (i do not use an engine during the lessons for obvious reasons), in the hope it would reveal why Ne7 is considered incorrect.

In most lessons potential moves can be rated (for want of a better word) as "alternate correct" moves. However in this situation it is not, according to the lesson Ne7 simply the wrong move. So i used the engine to look a little deeper into the position hoping to find out why Ne7 was incorrect, however both engines agreed Ne7 is the best move.

I all i was looking for was a discussion of the lesson, position and potential moves, after all is that not what the forums are for?