That's right. Comparing apples to apples (60 to 70) if you keep the same ratio of arrow weight to bow poundage the velocities should be similar.

I shoot all my 3D bows at 5 gr/lb. I get pretty near the same speeds at 53# as I used to get when I shot 67#. And the best part is I can shoot a harder cam without tearing my shoulders apart.

For a hunting setup it's still the same, keeping things in the proper ratio.
However, I don't agree that anything walking North America requires anything more than 60# anymore. All this equipment has improved over the last 30 years to a point that efficiency is sky high.

You know, 30 years ago a 70# bow was unheard of. With 20-25% letoff people just couldn't handle them. And there was a lot of heavy game shot back then. The bows of today are capable of about 30% more penetration "potential" just due to improvements in the equipment.
There's a lot of difference betweentoday's speed cam and a round wheel of yesteryear.