1. So instead of endgame position you show middlegame
2. While your example is a valuable one I don't see why to use it for demonstration of opening principles. It's much more natural to discuss those principles with a student during first 10-15 moves in annotated master game or while playing training game against him.
I show a point where both sides have to decide what exchanges to do.Exchanges are an important part of chess.
It is not natural to discuss about opening principles by showing openings.The reason is simple.Openings that clearly violate opening principles are good.
Take for example Scandinavian.The queen gets out early , Black loses tempi yet Scandinavian is fine.Why Scandinavian is fine although it violates several opening principles?Most opening parrots can't really answer that.
Or
Black has played only pawns and his queen.Why playing the queen with no piece developed?Doesn't that violate all opening principles?
If you want to superficially explain opening principles it is easy to do so.Everyone can do it.If you want more than that , then it's not so easy.
I am lost now. Do you suggest not to talk about opening principles at all because they have exceptions? Or you suggest to illustrate openings principles with examples from endgames because then problem of exceptions gets solved somehow? Isn't it a somewhat trivial fact that general principles have exceptions?
Every book that discusses opening principles does so by showing opening examples (including Capablanca!).
You don't even know the difference between Kan and Taimanov and I am the one that has poor understanding???
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You obviously have poor understanding of the English language.
Take a look at John Emms' excellent explanation of Qc7 in the Sicilian Taimanov in his award winning book, The Sicilian Taimanov: Move by Move pages 9 and 10.
You can look that page up for free on amazon.com:
http://www.amazon.com/gp/product/1857446828/ref=s9_simh_gw_g14_i1_r?ie=UTF8&fpl=fresh&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=desktop-1&pf_rd_r=18NZEVS6WDBHZ573KMDP&pf_rd_t=36701&pf_rd_p=2437869742&pf_rd_i=desktop
Of course, GM John Emms is probably wrong. He was merely an author of a book on the Sicilian Taimanov, but that's because he too has a poor understanding of the English language.
Taimanov himself called the system with Qc7 the Paulsen System. He considered his own system to involve Nge7. But he was the one to advance the ideas of Qc7 which is why it's usually called the Sicilian Taimanov: