This is only applicable for blindfolded simuls where one needs to remember all board configurations. If the GM (or the one providing simul) can see the board then he wouldn't need to track differences, he can simply play according to each board. Only in blindfold does he need to remember each configuration with perfect clarity so tiny differences can get very confusing.

Anyway, this reminds me of an anecdote I read long ago in a Tim Krabbe piece:

"A grandmaster once played a 10-board blind simul somewhere. Knowing the ropes of blind simuls, he varied his games right from the start, maybe opening two with 1.e4, two with 1.d4, one with 1.b3, and so on. To his suprise, all of his opponents played 1...b6. On the second move, five of them played 2...Bb7, and the other five 2...Ba6. On the third, three of the five players who had played 2...Bb7 now played 3...Bc8 and the other two played 3...Ba6, while three of the five who had played 2...Ba6 now played 3...Bb7, and the other two 3...Bc8. On move 4, the grandmaster saw bishops everywhere. After move 5, he excused himself and went to the toilet where he was happy to find a window big enough to let him through."

I think that's one of the anecdotes that I read regarding that strategy, but I didn't know it was from Krabbe.

I agree it probably works better in blindfold play, but it works well in normal simul too (I used it successfully once, though that wasn't against a GM, and I had fairly recently stopped playing competitive chess).

Now going way off topic, but Krabbe's cycling book "The Rider"[1] is probably the best book about cycling I've ever read. Along with "Once a Runner"[2] I think it probably the best piece of sporting fiction ever:

My whole life had only one goal: making that last wheel, here, now. I was wasted. But that elusive finish line, eight, seven, six and a half meters in front of me, kept my hope and desire awake. I coughed and slobbered. I remembered the words of advice ‘Shift, when you’re really, truly at the end of your rope, to a higher gear.’ I shifted. A few hysterical kicks on the thirteen, then clenched power of a mortal struggle. I was there. I was sitting on that last wheel. I was in the lead group.

[1] http://cyclingtips.com.au/2010/11/the-rider/

[2] http://www.slate.com/articles/arts/culturebox/2008/12/speed_...

An interesting question: What is the best strategy for a group of mediocre chess players against a grandmaster in simul?

Similar moves with small differences to encourage mistakes? Very different to make the mental switching harder? Very esoteric openings to avoid "played this a 1000 times" situations for the grandmaster?

Similar moves.

The GM's positional ability is almost certainly better than yours.