LOL, no idea what Steve-o was driving at. 5...b5 was played by Portisch and Torre, not just Smyslov. The move is okay, though rare.
Maybe Giddins was trying to justify Smyslov's loss in the game. Tony locked the black bishop in a cage in the game, and effectively blew Vassily awaaaaaaaayyyyy.
That he won the game doesn't mean that this particular decission was correct or not, lots of moves between move 5 and 41. I understand what 'usually' means. What I don't understand is the two comments in juxtoposition.
To give a move a ?! mark after suggesting it 1/2 ply before is, well, confusing. If it's a ?! move, why suggest it?
In the book 50 Essential Chess Lessons by Steve Gibbins, the following position occurs in the game between Miles-Smyslov, Dortmund 1986:
And after this posiiton Giddins has the commentary: "An unusual move. Generally White plays 5. a4, to prevent Black from hanging on to the extra pawn by . . . b5."Which is a perfectly understandable comment until the very next move, when we get:
"5. ... b5?!
It is naturally tempting to try to punish White for omitting a4, but the text move is certainly somewhat risky. Simply, 5. ... Nbd7 6. Nxc4 b4 gives black a good game."
So that leads me to a question: What the heck?! Should white play a4 to prevent b5 as the comment on the white half of the move suggest? And if white doesn't need to prevent b5 (as the black half of the move suggests) what should white play?
It's like two different people wrote those comments, because they seem to be mutually exclusive statements.