I wouldn't want to comment whether that's part of Sniper theory or otherwise.John McKenna wrote:I see that it's touched on (a single game) in The Modern Defence by McDonald & Speelman - 1.d4 g6 2.c4 Bg7 3.Nc3 c5 4.d5 then f5!? (Norwood) 5.h4!? Bc3+... 0-1 (29) Bacrot-Speelman 1998 Elista Olympiad.
After 6 bxc3 Nf6, there are more games than you might expect, so it's a main line known to at least some players. The popular moves next are 7 h5 Rg8 which are logical if bizarre. Other than the original Speelman game and a game by Ian Rogers at Gibraltar, I didn't find any British examples.