To simplify this and try and keep from getting all tangled up like a bowl of spaghetti The phrase I read in your post was:
"Penetration does not depend on velocity, just boolit weight and the integrity of the boolit."
My reply:
How could anyone argue that a 45ACP shooting a 250 grain bullet at 800fps could exceed the lethal performance from the same style bullet going 1600fps from a 454?
My point is velocity matters by a significant margin YMMV
Okay, I'll take a stab at it. Given your example above, of course, I must agree. At some point however, dead is dead, and enough is enough. My South African friend has shot quite of bit of plains game and is an avid reloader (in spite of the difficulty of doing so currently). He told me that an impact velocity of 2200-2400 was considered optimal for large dangerous game there. Any more was considered undesireable. I realize this conclusion may be based on the physics of bullet failure, and stuff like Barnes X's may render this conclusion false, but wouldn't the same principal apply to a cast lead bullet, at some point?
