Again, it's just s matter of taste.
I still see nothing wrong at all with ...Nf6 and ...Nc6.
Not sure why it bothers you so much.
6...Nf6 is 100% not a critical move or major mistake or anything like that. I'm just giving my impression that it's a move by a player who is not playing with any particular plan in mind.
I'm not saying it's either knights on f6/d7 or c6/e7. Nf6 isn't even wrong in very similar positions. Every pawn move included or excluded changes things.
For example one thing that comes to mind is there's no pawn on e4, so I'm reluctant to treat it like a KID in the first place. I'd rather try a pawn break against the c pawn (probably d5).
There's also no pawn on e3 blocking a move like Bg5. Maybe I'd rather play Nf6 after that's no longer a possibility. Also there's no pawn on d3, so white can still play d4 in one move. So after d3 maybe I wouldn't be uncomfortable with Nf6 which blocks control of d4.
White was being very flexible and quick with his queenside expansion plan, black needs to be accurate to survive, especially against a GM... and just look at the position after 10...Nd7. Can you guess which player is the GM from that position alone? Does it look like black made no mistakes?
The point being, sometimes just making normal looking moves and hoping to come up with a plan later doesn't work out.
Oh yeah, it is like a reversed sicilian. That's probably where my pattern recognition is coming from. I used to play 2.Nc3 with 3.g3 against the sicilian... and I always put my king's knight on e2.
My example game for handling the queenside expansion went knight from c3 to d1 (covering b2 from the bishop) and then breaking in the center with c3 and d4.
edit, crap, I said 2.Nf3, I mean to say 2.Nc3 for the closed sicilian.
So yeah, Nc6 is fine, but I don't recognize it in conjunction with some kind of Nh5 f5-f4 plan. The f4 break is normal-ish looking, and is probably fine most of the time, at least against lesser players (I didn't see any of those GMs go for it like I mentioned earlier).
I never heard this rule of thumb before. To me it's just a matter of taste.
All I see is a KID vs an English.
GM got an edge with White and increased it because he's a GM.