I am really surprised this didn't kick up

Lots of debatable info.Flex was definately a part of engineering our vehicles.They used to say a Model A would flex through any rough road of the day and that is why their frames weren't boxed.
Think of a long piece of steel and apply weight to the centre...it will form a smooth gradual bend.Now reinforce the centre 50% and apply the weight again and you will probably break the ends off.
I don't think it will matter for the majority of us one way or the other.