> You seem to be talking about compile-time versus runtime

Yes 100%! I was talking runtime in reference to Ruby and later Python.

> That seems to harm rather than help your previous claim. In untyped languages, in principle every object has to be treated as dynamic.

It is rather confusing and even counterintuitive, but being dynamic does not mean a language must also be untyped. For example, Python is both strongly typed and dynamically typed at once. [1] It's objects have a definitive type, but you can swap out objects of any type out at any time (a=1 ... a="foo") using the same variable. That makes optimization rather tricky as you can imagine.

1 - https://wiki.python.org/moin/Why%20is%20Python%20a%20dynamic...

> I've not even heard of compile times being significantly slowed by type checking.

Look at Swift. But yeah, Swift is the only language I've ever heard having compile time issues because of the type checking.