Then again, I find it very hard to undestand that even chess professionals commonly don't use the alternative move orders for White.
Why are the alternative move orders not much more popular at master level in order to avoid a very dangerous black weapon?

I would just be shocked if the answer really was that most of them don't know of the more sophisticated white move order...  

Hello everybody,

the Modern Benoni has been my preferred choice against 1.d4 ever since I started getting a better and more aggressive player (at the age of 13). By now I have reached an ELO rating of 2300 and still use this opening in a large number of my (black) games.

However, there is one particular aspect of that opening that still leaves me wondering even today. Let me explain step by step:

The variation 1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.Nf3 g6 7.e4 a6(!) - or 6.e4 g6 7.Nf3 a6(!) - is scoring unbelievably well for Black in practice. This very line was advocated by J. Watson in his well-known book "The Gambit Guide to the Modern Benoni", and it has also served me well over the years.

It was clear to me that White has a clever way to bypass this variation if he intends to reach the Modern main line (Nc3, e4, Bd3, Nf3, h3), namely: 1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.e4 g6 7.Ld3! - rendering the Bg4-idea of the a6-variation above useless! - 7...Bg7, and only now 8.h3! and 9.Nf3. In fact, as a 1.d4-player I commonly use this exact sequence as White.
So far, so good.

Lately, I played an IM who also used the above-mentioned move order against me to get to the Modern Main Line. After the game (which he won), he asked me why I played the a6-variation at all, as White could reach the Modern Main Line via the other move-order anyway.
When I told him that the a6-variation did at least prevent White from reaching the Classical Main Line (1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.Nf3 g6 7.e4 Bg7 8.Be2), HE TOLD ME THAT THIS WAS IN FACT NOT THE CASE.
By starting with the knight's tour variation, White has a bulletproof way of reaching the Classical. At first, I couldn't believe this was true, but a quick analysis with some opening databases confirmed his assessment.
Having never encountered the Knight's Tour Variation in a practical game, these new kinds of problems had thus never occured to me before.

Now however, I am actually shocked. Is the whole a6-variation really only counting on the white player's ignorance of how to reach his desired variation?? I find that hard to believe, but yet... I do not see any other explanation...
Obviously one could argue that White allows Black to deviate with ...a6 at free will because he regards that variation as bad, but as Black scores even above 50% in the a6-line this cannot be the reason of course.
How about the famous Van Wely-Topalov encounter in the a6-variation for example: If Topalov had played 7...Bg7 instead of 7...a6 he would have forced White to play either the Classical or the Modern Main Line. So, whatever line the Dutch superstar would have played, why didn't he go for 1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.e4 g6 7.Ld3!, 8.h3, 9.Nf3 (--> Modern ML) or 1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.Nf3 g6 7.Nd2! Bg7 8.e4, 9.Be2, 10.0-0 (--> Classical ML) instead, limiting Topalov's options?!!

Is there something more to be said - am I missing something?? Please help me if you can!