This is just incredibly untrue. I'm supposing you've never played high level sports or trained with professionals over an extended period of time. Training in today's world is so much more than lifting weights and absolutely increases all athletic functions. Furthermore most trainers work to enhance genetic strengths.
I guess you'll enlighten us then?
His versatility is legit. It could turn him from a good player to a great one and I think it raises his floor considerably.
It means you can play close to the basket, especially defensively, and not be an embarrassment. Means you need to rebound, challenge shots, and be strong enough to body up players your size. If you can't do this (and the jury is still out), you're a glorified Ryan Anderson or Kelly Olynyk.
I'm not sure what to say about your list of playoff PFs. Many of those don't have the talent level to be mentioned in the same sentence with the 3rd pick. The most notable ones rebound and/or block shots.
I know you can't be convinced, but the playoff power forwards are proof positive of what works in the modern NBA. They are key cogs in the modern NBA offense in order to open the court up, even if they aren't scoring a lot.
If that forward can also shoot, attack closeouts, and distribute on pick-and-rolls, the offense becomes even more deadly. If they can switch on defense (because the switching neutralizes the stretch fours strength while also not losing solid defense on ball), then that scheme is extremely frustrating for offenses.
The key for Bender will be whether or not he can take advantage of matchups, and whether or not he can hold his own on defense against the minimal postup attempts in the modern NBA. I think he can. I also would like to have someone who can defend the rim in help situations. Again, I think he can learn that.