I am pleased you did not take offense, because certainly no offense was intended. Just a gentleman's disagreement based on different bowhunting experiences and observed results.
In regard to Ashby's theory of broadhead design, I certainly do not take Ashby's work as Gospel. However, the data he provides (especially his latest work) is a very credible resource because his testing is done utilizing widely recognized scientific methods and standards. His studies and experiments are based on basic physics and engineering principles which has revealed some compelling data that I have applied with great success in my own bow hunting experiences. Especially in recent years where I have come nearly full circle from shooting lighter, faster arrows back to slower, heavier arrow builds with above average FOCs. The drastic increase in penetration I have personally experienced with both mine and my wife's set-ups are really undeniable.
The pros & cons of a long, narrow versus a short, wider broadhead design applied on heavy-boned African game and Cape buffalo in particular, is certainly debatable. Ashby's claim is that a longer, narrower design has demonstrated to have less drag than a shorter, wider design. Less drag equals less momentum-robbing surface tension translating to better penetration. If I am understanding you correctly, the failures of these longer, narrower designs that you have witnessed are attributed to lateral movement of the arrow on impact which would be a tuning issue and not necessarily a broadhead design flaw. Failures or poor penetration due to improper tuning are no more a fault of the components than poor shot placement.
It's also important to consider the overall poundage draw of the bow into the equation. If the hunter is capable of drawing 80+ pounds, that makes up for a lot of KE that would neutralize any momentum loss generated from the friction of a wider broadhead design. Ashby's physical findings definitively suggest many more applicable mechanical advantages for those hunters who can only shoot lower poundage bows.
You also noted in an earlier post that you had good success with the Steelforce? Not sure which Steelforce design you liked, but all of the Steelforce designs that are solid, single bevel designs intended for big game are patterned as a long, narrow designs which are almost copycats of the Ashby design...? So, if it's the design and not the material, you have me a bit confused.
Good discussion and debate in any case. I always find contrasting experiences beneficial as a learning tool assuming the data and methods used are consistent.