Have you not seen zillions make opening moves in regular chess? That is the type of 'chess' engines played unless they have some sophisticated opening book/algorithm built in.
We are not talking simple e4 /e5 here we are talking about opening plans 20 moves deep as in a Ruy Lopez, a Sicilian -- what program has come up with something as detailed?
I am not criticizing your engine - and I understand that NO ONE has developed any opening book for capablanca chess ..
But you cannot expect your engine to make complex strategical decisions (esp in the opening) unless you program it that way ..
In any case, you have misunderstood my point - Lets say you try the same thing with 8x8 chess and one is the std setup. Your machine might pick up tactical threats but it certainly will NOT play the openings very well as least in comparison to a GM (std chess setup of course)
Do you realize that it took at least 100 yrs + to get opening theory where it is now? There is no program ever made that could ever come up with anything close to it.
Even Rybka plays very questionable lines when opening book is completely removed
IN any case your experiment is still useful in throwing out some setups - greater tactical threats will pressure a human player even more.
But given time, humans can certainly come up with better ways to play the opening than your engine can by itself esp for the first 10-15 moves. This may or may not change your results but that was not my point of contention.