Are a Ruger GP100 and S&W 686 essentially the same gun?
Both are stainless, DA, L-frame (not called that by Ruger, but very similar dimensions) .357 revolvers that can be had with short barrels or 6" barrels. Both will accept a fairly wide variety of grip shapes. Both have cylinders that even rotate the same direction (unlike Colts).
Should it matter that one has a sideplate, and the other allows access to innards via the trigger guard? Should it matter that one has a fore-and-aft cylinder release, and the other has a toggle? I mean, they're really the same gun, right?
Meanwhile, RickB, you want to attack those factors I listed between CZ75 and BHP that you find to be merely cosmetic, such as slight differences in width, or how the slide and frame are fitted.
You keep avoiding the fact that the BHP is a single action mechanism, with a fairly stiff break and short reset, while the CZ75 is a double action mechanism that also allows single action mode, with a more rolling break and a fairly long reset. (Unless you limit the CZ75 under discussion to the SA only model, in which case the break and reset are still different.)
Shoot the two side by side, and you won't call one a copy of the other. They are very different; their only similarities, other than grip shape (and the CZ is thicker, there, too) are cosmetic.