This is why david is our favorite non mod!
I think what he may be trying to say is that in a perfect world, you will have no trouble what so ever killing deer and blowing right through them. But, the world is an imperfect place, and crap happens. I shoot 74 pounds of KE and only got about 8" of penetration once. That was due to ribs and the offside shoulder blade. The blade on a deer is quite thick, and while you can punch through it w/ a good head, most times you just don't.
So, to maximize effectiveness on the imperfect shots, KE needs to be maximized to give us the little help we need for that situation. You hear the trad guys talk about it a lot, but that's because their equipment just doesn't have the power ours does. OK, before you trad guys jump my butt, let me say that I have a world of respect for ya. No way I could do it, I'm just not that good.
David was also just making sure you had the correct information you need to be the best bowhunter you can be. Alot of guys walk around w/ bows in hand and have ABSOLUTELY no idea what they are shooting, let alone the efficiency and so forth. One way to be the best you can be is to be is to have the correct information. He merely saw a discrepency and pointed it out, not intending to insinuate you didn't know what you're talking about.