In our own case here and now, we are actually failing to understand each other fully because I can't show you actual videotapes of what I'm talking about.

What do you mean by "fully" ? I believe I understand you well enough for all practical purposes. I don't agree with you, but agreement and understanding are two different things.

First, I don't contest the existence of verbal labels that merely refer -- or even just register as being invoked without refering at all.

I'm not sure what you mean by "merely refer", but keep in mind that we humans are able to communicate concepts which have no physical analogues that would be immediately accessible to our senses. For example, we can talk about things like "O(N)", or "ribosome", or "a^n +b^n = c^n". We can also talk about entirely imaginary worlds, such as f.ex. the world where Mario, the turtle-crushing plumber, lives. And we can do this without having any "physical context" for the interaction, too.

All that is beside the point, however. In the rest of your post, you bring up a lot of evidence in support of your model of human development. That's great, but your original claim was that any type of intelligence at all will require a physical body in order to develop; and nothing you've said so far is relevant to this claim. True, human intelligence is the only kind we know of so far, but then, at one point birds and insects were the only self-propelled flyers in existence -- and that's not the case anymore.

Furthermore, your also claimed that no simulation, no matter how realistic, will serve to replace the physical world for the purposes of human development, and I'm still not convinced that this is true, either. As I'd said before, we humans do not have perfect senses; if physical coordinates of real objects were snapped to a 0.01mm grid, no human child would ever notice. And in fact, there are plenty of humans who grow up and develop language just fine without the ability to see colors, or to move some of their limbs in order to point at things.

Just to drive the point home: even if I granted all of your arguments regarding humans, you would still need to demonstrate that human intelligence is the only possible kind of intelligence; that growing up in a human body is the only possible way to develop human intelligence; and that no simulation could in principle suffice, and the body must be physical. These are all very strong claims, and so far you have provided no evidence for any of them.