No. The cast iron block is so beefy because it was originally engineered to be structurally adequate in either aluminum or iron. That is one fact we have directly from the mouth (pen) of the engineer in charge of the project. While nobody can dispute the significant differences between the aluminum block and the iron block, none of them bears on the bottom-end beefiness of the engine. The skirt depth is the same: adequate in aluminum, way more than adequate in iron—for one example. :-)
You can be as info-resistant as you want, and you're welcome to believe whatever made-up nonsense you want to believe, but all it does is make you look like you're sitting there with your fingers in your ears and your hands over your eyes doing the equivalent of "La la la can't hear you don't see you la la la myth myth myth, it's beefy because things were beefy back then la la la". Me, I think I'll put more weight on "This is why we did it" from the guy who was in charge of doing it, than I'll put on "Kesteb said nuh-uh". :-)
Also remember that over the years the block got lighter.
