There is a significant difference between this 1905 model and the 1903 plane. The stability in pitch increased significantly. The 1909 (1905) airplane had also dihedral stability (auto roll control) while the 1903 machine did not have. We talk about two sensible different airplanes having two totally different engines. Just because the 1909 model was flyable it does not automatically mean the 1903 plane could take off and fly stably.
No 5hit 5herlock...it is called development...funnily enough this is still going on in aircraft design...the perfect aircaft has still not been built and even in fairly recent times the first flight of an aircraft has been a fairly fraught affair
I am sure the Wrights would agree that the 1903 Flyer was imperfect...which is why they redesigned/improved it for the 1905 flights,they did have a self built wind tunnel - and remember not many people at that time knew much about stability etc