It's always been a system used by white and black. I noticed that black playing a London was referred to as a reversed London but it's arguable that the reversed London is the London played by white. That's because it's primarily a defensive system, which was commonly played by the black side.
the london system i think is a reversed slav, the only reason why black takes on c4 in the slav is to win a tempo on the bishop and release some central pressure
Asking how to play a Grunfeld against the London is like asking how to play the Najdorf against 1. c4. It doesn't work that way. Pawn structures are different, piece placement is different, ideas are different.
no! the Grunfeld defense is against d4 and even c4, so there's a way to play grunfeld against London, and you confuse it after 1 c4, you don't play Narjdorf because it's an opening with white, in this case you can play the Sicilian defense that is symmetrical. Your comment doesn't make any sense, but thanks!
It did make sense, you just didn’t understand it.
care to explain??
I don't think so. Svidler isn't an "elite playsr" but he presumably is one of the large pool of players trying also to earn a living through chess. Since the largest majority of people paying for courses or coaching are at quite a low playing ability but maybe with some money, all people in this pool have to do is make noises that seem coherent even if they aren't.
Hmm, I can't imagine describing Peter Svitler as not an elite player. Peter Svidler, who's won the Russian Championship eight (!) times. Peter Svidler, who's played in the Candidates three times,. Peter Svidler, who tied for second in a World Championship tournament and won a World Cup. Etc., etc., etc. Especially in the context of the Gruenfeld, an opening where he's probably the greatest expert alive (with the possible exception of MVL, but Svidler's been playing it longer).
But on the bigger point, I agree with you. Without White playing c4, it's not a Gruenfeld, nor even, in any meaningful way, a Gruenfeld setup. The Gruenfeld depends on that pawn tension and the possibility for the center to open up. (And "Gruenfeld System" is a meaningless phrase -- some openings, like the London -- are systems that can be played against anything, but the Gruenfeld is highly concrete.)
Someone else who probably agrees with you is ... Peter Svidler. I don't have his full course, but here's his explanation of why he recommends Black answer 1. d4 Nf5 2. Bf4 with 2. ... g6:
"We're playing 2...g6 for one major reason. White can start with 2.Nf3, and as honorable Grünfeld aficionados, we're obliged to reply with 2...g6, which, after 3.Bf4, locks us into the fianchetto setups. Therefore, I feel that spending time to learn the other replies to 2.Bf4 is, let's say, an unnecessary investment of time and effort on both mine and your part."
In other words, he's not saying that you should play a fianchetto setup against the London in order to play a "Gruenfeld setup" against it specifically; he's pointing out that Gruenfeld players have to be able to play a fianchetto setup against the London because of specific move-order tricks.