K-5 Program mode settings
Yes, I quite agree that this is a great explanation that Pentax should have included in the manual. Too late for that I fear, however they could do an article on it on their web site.
I've determined myself, that in auto aperture depends on focussing distance, however I did not manage to notice dependency on focal lenngth. Excellent observation and explanation, Pentax should include your explanation into their user manuals.