Standard, of course, is 6.Bb5 Ne4 7.Nxd4 Bd7 8.Bxc6 bxc6 when White has good play either on the weakened dark squares on the Queenside with Be3, Nb3, and Qd2-c3 or by attacking on the Kingside with f2-f4-f5. Marshall writes, "The move in the text is bad; in fact, this Bishop is completely out of the game." Once Black commits to blocking up the center with pawns on light squares, White does best to exchange the Bishop for a Knight rather than sideline it at b3.
Accepting White's gambit with 7....dxc3 8.Bxd5 cxb2 may allow him chances to equalize after 9.Bxc6+ bxc6 10.Qxd8+ Kxd8 11.Bxb2 due to the doubled pawns on the open c-file. Black's choice retains the initiative and still keeps White from easily recovering the pawn.
"A powerful move," writes Marshall, that "shows clearly how inadequately White has developed."
Howell notes that 17....Ng3+ was threatened, and if the Queen tries to escape from the indirect attack by the Bishop at f5 with either 17.Qd1 or 17.Qb5 then 17....Nxc3 is a powerful fork. Also, "17.Bxc6 will not do because of 17....Ng3+ 18.Kg1 (otherwise the Queen goes with a check) 18....bxc6 etc." White will pick up the exchange with a winning game.
Marshall writes, "After this it is all over. Black's position soon takes its toll."
Or 22.Qd2 Rxf3 23.Kxh1 Bxg2!+ 24.Qxg2 Rh3+ notes Howell.
Howell writes, "As the Bishop cannot be captured, Black must win easily."