There is one advantage the lower rated player has over the higher rated one: the 'draw threat'. A draw kinda looks bad, and takes a chunk out of the stronger's rating, whilst the weaker gets a boost. Now, superkids on the make are seriously dangerous opponents, as they are stronger than their ratings and are still finding their level.

I like this line for White, but to be honest, in the old days I used to dodge the Grunfeld altogether as White. You can if you play the English...  

Yes it does! For instance after 1.e4 b6 2. d4 Bb7 3. Bd3 for years 3....f5 was considered black's best move. Now it is considered a blunder.

I didn't know that theory, but why anyone could suppose 3...f5 in that line was OK, I can't imagine. 4.exf5 and White already has much the better of it!

The one time I found myself in a Grunfeld, I wanted to play 7.Bc4, but in my inexperience, thought it would be criticised, and played 7.Nf3 instead. It turns out it is quite playable, but I didn't know that, got myself in a tangle, dropped a pawn, and barely managed to scramble a draw with a heavy piece attack down the h-file. Not one of my shininger moments... On Gameknot, I once tried 7.f4 by way of an experiment. I won the game, but only because my opponent blundered in the Queen and pawn end game.game

Black could strike at the centre at once by 7...c5.

Because he has just moved his knight to f3 instead of e2

This is the move, sooner or later, that keeps Black in the game.

9...Qa5 would place White's centre left under a fair bit of pressure...

This was the move that vexed me so much about having played Nf3. The threat is to exchange on f3, forcing White to recapture with the g-pawn, on pain of losing the d-pawn. These days, that wouldn't bother me too much, but forty-three years ago it did.

More to force the queens off.

I think I would have preferred 13.Nxd2 Bxe2 14.Kxe2 ... with a slightly more solid position.